Power tool having a universal motor capable of being powered by AC or DC power supply

ABSTRACT

A power tool is provided including an electric universal motor configured to operate within an operating voltage range of approximately 90V to 132V. A power supply interface is arranged to receive at least one of Alternating Current (AC) power from an AC power supply having a first nominal voltage or Direct Current (DC) power from a DC power supply having a second nominal voltage, where the first and second nominal voltages fall approximately within the operating voltage range of the motor. The power supply interface is configured to output the AC power via an AC power line and the DC power via a DC power line. A motor control circuit supplies electric power from one of the AC power line or the DC power line via a common node to the motor such that the motor brushes are electrically coupled to one of the AC or DC power supplies.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/289,654 filed Oct. 10, 2016, titled “Power Tool Having Multiple PowerSupplies,” which is a continuation of PCT Application No.PCT/US2015/031432 filed May 15, 2015, titled “Power Tool System,” and ofU.S. patent application Ser. No. 14/992,484 filed Jan. 11, 2016, titled“Power Tool System,” which claims the benefit of U.S. patent applicationSer. No. 14/715,258 filed May 18, 2015, titled “Power Tool System,” allof which claim priority, under 35 U.S.C. § 119(e), to U.S. ProvisionalApplication No. 61/994,953, filed May 18, 2014, titled “Power ToolSystem,” U.S. Provisional Application No. 62/000,112, filed May 19,2014, titled “Power Tool System,” U.S. Provisional Application No.62/046,546, filed Sep. 5, 2014, titled “Convertable Battery Pack,” U.S.Provisional Application No. 62/118,917, filed Feb. 20, 2015, titled“Convertible Battery Pack,” U.S. Provisional Application No. 62/091,134,filed Dec. 12, 2014, titled “Convertible Battery Pack,” U.S. ProvisionalApplication No. 62/114,645, filed Feb. 11, 2015, titled “Transport forSystem for Convertible Battery Pack,” U.S. Provisional Application No.62/000,307, filed May 19, 2014, titled “Cycle-By-Cycle Current Limit forPower Tools Having a Brushless Motor,” and U.S. Provisional ApplicationNo. 62/093,513, filed Dec. 18, 2014, titled “Conduction Band Control forBrushless Motors in Power Tools,” each of which is incorporated byreference.

TECHNICAL FIELD

This application relates to a power tool system that includes variouspower tools and other electrical devices that are operable using variousAC power supplies and DC power supplies.

BACKGROUND

Various types of electric power tools are commonly used in construction,home improvement, outdoor, and do-it-yourself projects. Power toolsgenerally fall into two categories—AC power tools (often also calledcorded power tools) that can operate using one or more AC power supply(such as AC mains or a generator), and DC power tools (often also calledcordless power tools) that can operate using one or more DC powersupplies (such as removable and rechargeable battery packs).

Corded or AC power tools generally are used for heavy duty applications,such as heavy duty sawing, heavy duty drilling and hammering, and heavyduty metal working, that require higher power and/or longer runtimes, ascompared to cordless power tool applications. However, as their nameimplies, corded tools require the use of a cord that can be connected toan AC power supply. In many applications, such as on construction sites,it is not practical to connect to an AC power supply and/or AC powermust be generated by a separate AC power generator, e.g., a gasolinepowered generator.

Cordless or DC power tools generally are used for lighter dutyapplications, such as light duty sawing, light duty drilling, fastening,that require lower power and/or shorter runtimes, as compared to cordedpower tool applications. Because cordless tools may be more limited intheir power and/or runtime, they have not generally been accepted by theindustry for many of the heavier duty applications. Cordless tools arealso limited by weight since the higher voltage and/or capacitybatteries tend to have greater weight, creating an ergonomicdisadvantage.

AC power tools and DC power tools may also operate using many differenttypes of motors and motor control circuits. For example, corded or ACpower tools may operate using an AC brushed motor, a universal brushedmotor (that can operate using AC or DC), or a brushless motor. The motorin a corded tool may have its construction optimized or rated to run onan AC voltage source having a rated voltage that is approximately thesame as AC mains (e.g., 120V in the United States, 230V in much ofEurope). The motors in AC or corded tools generally are controlled usingan AC control circuit that may contain an on-off switch (e.g., for toolsoperating at substantially constant no-load speed) or using a variablespeed control circuit such as a triac control circuit (e.g., for motorstools operating at a variable no-load speed). An example of a triaccontrol circuit can be found in U.S. Pat. No. 7,928,673, which isincorporated by reference.

Cordless or DC power tools also may operate using many different typesof motors and control circuits. For example, cordless or DC power toolsmay operate using a DC brushed motor, a universal brushed motor or abrushless motor. Since the batteries of cordless power tools tend to beat a lower rated voltage than the AC mains (e.g., 12V, 20V, 40V, etc.),the motors for cordless or DC power tools generally have theirconstruction optimized or rated for use with a DC power supply havingone or more of these lower voltages. Control circuits for cordless or DCpower tools may include an on-off switch (e.g., for tools operating atsubstantially constant no-load speed) or a variable speed controlcircuit (e.g., for tools operating at a variable no-load speed). Avariable speed control circuit may comprise, e.g., an analog voltageregulator or a digital pulse-width-modulation (PWM) control to controlpower delivery to the motor. An example of a PWM control circuit can befound in U.S. Pat. No. 7,821,217, which is incorporated by reference.

SUMMARY

In an aspect, a power tool system includes a first power tool having alow power tool rated voltage, a second power tool having a medium powertool rated voltage that is higher than the low power tool rated voltage,a third power tool having a high power tool rated voltage that is higherthan the medium power tool rated voltage, a first battery pack having alow battery pack rated voltage that corresponds to the low power toolrated voltage, and a convertible battery pack. The convertible batterypack is operable in a first configuration in which the convertiblebattery pack has a convertible battery pack rated voltage thatcorresponds to the first power tool rated voltage, and in a secondconfiguration in which the convertible battery pack has a secondconvertible battery pack rated voltage that corresponds to the secondpower tool rated voltage. The first battery pack is coupleable to thefirst power tool to enable operation of the first power tool. Theconvertible battery pack is coupleable to the first power tool in thefirst configuration to enable operation of the first power tool. Theconvertible battery pack is coupleable to the second power tool in thesecond configuration to enable operation of the second power tool. Aplurality of the convertible battery packs are coupleable to the thirdpower tool in their second configuration to enable operation of thethird power tool.

Implementations of this aspect may include one or more of the followingfeatures. The third power tool may be alternatively coupleable to an ACpower supply having a rated voltage that corresponds to a voltage ratingof an AC mains power supply to enable operation of the third power toolusing either the plurality of convertible battery packs or the AC powersupply. The AC mains voltage rating may be approximately 100 volts to120 volts or approximately 220 volts to 240 volts. The high power toolrated voltage may correspond to the voltage rating of the AC mains powersupply. The system may further include a battery pack charger having alow charger rated voltage that corresponds to the low battery pack ratedvoltage and to the convertible battery pack rated voltage, wherein thebattery pack charger is configured to be coupled to the first batterypack to charge the first battery pack, and to be coupled to theconvertible battery pack when in the first configuration to charge theconvertible battery pack.

The medium power tool rated voltage may be a whole number multiple ofthe low power tool rated voltage, and the high rated power tool ratedvoltage may be a whole number multiple of the medium power tool ratedvoltage. The low power tool rated voltage may be between approximately17 volts to 20 volts, the medium power tool rated voltage may be betweenapproximately 51 volts to 60 volts, and the high power tool ratedvoltage may be between approximately 102 volts to 120 volts. The firstpower tool may have been on sale prior to May 18, 2014, and the secondpower tool and the third power tool may have not been on sale prior toMay 18, 2014. The first power tool may be a DC-only power tool, thesecond power tool may be a DC-only power tool, and the third power toolmay be an AC/DC power tool.

The convertible battery pack may be automatically configured in thefirst configuration when coupled to the first power tool and may beautomatically configured in the second configuration when coupled to thesecond power tool or the third power tool. The system may include athird battery pack having a medium battery pack rated voltage. The thirdbattery pack may be coupleable to the second power tool to enableoperation of the second power tool. A plurality of third battery packsmay be coupleable to the third power tool to enable operation of thethird power tool. The first battery pack may be incapable of enablingoperation of the second power tool or the third power tool.

In another aspect, a power tool system includes a first battery packhaving a first battery pack rated voltage and a convertible battery packoperable in a first configuration in which the convertible battery packhas a first battery pack rated voltage and in a second configuration inwhich the convertible battery pack has a second convertible battery packrated voltage that is higher than the first convertible battery packrated voltage. A first power tool has a first motor, a first motorcontrol circuit, and a first power supply interface. The first powertool has a first power tool rated voltage that corresponds to the firstbattery pack rated voltage and the first convertible battery pack ratedvoltage. The first power tool is operable using either the first batterypack when the first power supply interface is coupled to the firstbattery pack or using the convertible battery pack when the first powersupply interface is coupled to the convertible battery pack so that theconvertible battery pack is in the first configuration. A second powertool has a second motor, a second motor control circuit, and a secondpower supply interface. The second power tool has a second power toolrated voltage that corresponds to the second convertible battery packrated voltage. The second power tool is operable using the convertiblebattery pack when the second power supply interface is coupled toconvertible battery pack so that the convertible battery pack is in thesecond configuration. A third power tool has a third motor, a thirdmotor control circuit, and a third power supply interface. The thirdpower tool has a third rated voltage that is a whole number multiple ofthe second convertible battery pack rated voltage. The third power toolis operable using a plurality of the convertible battery packs when thethird power tool interface is coupled to the plurality of convertiblebattery packs so that the convertible battery packs each are in thesecond configuration.

Implementations of this aspect may include one or more of the followingfeatures. The third power supply interface of the third power tool maybe alternatively coupleable to an AC power supply having a rated voltagethat corresponds to a voltage rating of an AC mains power supply toenable operation of the third power tool using either the plurality ofconvertible battery packs or the AC power supply. The AC mains voltagerating may be approximately 100 volts to 120 volts or approximately 220volts to 240 volts. The high power tool rated voltage may correspond tothe voltage rating of the AC mains power supply.

The system may include a battery pack charger having a first chargerrated voltage that corresponds to the first battery pack rated voltageand to the first convertible battery pack rated voltage. The batterypack charger may be configured to be coupled to the first battery packto charge the first battery pack, and to be coupled to the convertiblebattery pack when in the first configuration to charge the convertiblebattery pack. The second power tool rated voltage may be a whole numbermultiple of the first power tool rated voltage. The first power toolrated voltage may be between approximately 17 volts to 20 volts, thesecond power tool rated voltage may be between approximately 51 volts to60 volts, and the third power tool rated voltage is betweenapproximately 100 volts to 120 volts. The first power tool may have beenon sale prior to May 18, 2014, and the second power tool and the thirdpower tool may have not been on sale prior to May 18, 2014.

The first power tool may be a DC-only power tool. The second power toolmay be a DC-only power tool. The third power tool may be an AC/DC powertool. The convertible battery pack may be automatically configured inthe first configuration when coupled to the first power tool and may beautomatically configured in the second configuration when coupled to thesecond power tool or the third power tool. The system may include athird battery pack having a third battery pack rated voltage thatcorresponds to the second power tool rated voltage. The third batterypack may be coupleable to the second power tool to enable operation ofthe second power tool and a plurality of third battery packs may becoupleable to the third power tool to enable operation of the thirdpower tool. The first battery pack may be incapable of enablingoperation of the second power tool or the third power tool.

In another aspect, a power tool includes a power supply interface, amotor, and a motor control circuit. The power supply interface isconfigured to receive AC power from an AC power supply having a rated ACvoltage that corresponds to an AC mains rated voltage, and to receive DCpower from one or more removable battery packs having a total rated DCvoltage that also corresponds to the AC mains rated voltage. The motorhas a rated voltage that corresponds to the rated AC voltage and to therated DC voltage. The motor is operable using both the AC power from theAC power supply and the DC power from the DC power supply. The motorcontrol circuit is configured to control operation of the motor usingone of the AC power and the DC power, without reducing a magnitude ofthe rated AC voltage, without reducing the magnitude of the rated DCvoltage, and without converting the DC power to AC power.

Implementations of this aspect may include one or more of the followingfeatures. The rated AC voltage may be between approximately 100 voltsand 120 volts. The DC rated voltage may be between approximately 102volts and approximately 120 volts. The motor rated voltage isapproximately 100 volts and 120 volts. The rated AC voltage mayencompass an RMS voltage of 120 VAC and the rated DC voltage mayencompass a nominal voltage of 120 volts. The rated AC voltage mayencompass an average voltage of approximately 108 volts and the rated DCvoltage may encompass a nominal voltage of approximately 108 volts. TheAC power supply may include AC mains.

The one or more removable battery packs may include at least tworemovable battery packs. The at least two battery packs may be connectedto each other in series. Each battery pack may have a rated DC voltagethat is approximately half of the rated AC voltage. The motor may be auniversal motor. The control circuit may be configured to operate theuniversal motor at a constant no load speed. The control circuit isconfigured to operate the universal motor at a variable no load speedbased upon a user input. The motor may include a brushless motor.

In another aspect, a power tool system includes a DC power supply and apower tool. The DC power supply includes one or more battery packs thattogether have a rated DC voltage that corresponds to an AC mains ratedvoltage. The power tool has a power supply interface, a motor, and amotor control circuit. The power supply interface is configured toreceive AC power from an AC power supply having the AC mains ratedvoltage and to receive DC power from the DC power supply. The motor hasa rated voltage that corresponds to the AC mains rated voltage and tothe rated DC voltage. The motor is operable using both the AC power fromthe AC mains power supply and the DC power from the DC power supply. Themotor control circuit is configured to control operation of the motorusing one of the AC power and the DC power, without reducing a magnitudeof the rated AC voltage, without reducing the magnitude of the rated DCvoltage, and without converting the DC power to AC power.

Implementations of this aspect may include one or more of the followingfeatures. The rated AC voltage may be between approximately 100 voltsand 120 volts. The DC rated voltage may be between approximately 102volts and approximately 120 volts. The motor rated voltage isapproximately 100 volts and 120 volts. The rated AC voltage mayencompass an RMS voltage of 120 VAC and the rated DC voltage mayencompass a nominal voltage of 120 volts. The rated AC voltage mayencompass an average voltage of approximately 108 volts and the rated DCvoltage may encompass a nominal voltage of approximately 108 volts. TheAC power supply may include AC mains.

The one or more removable battery packs may include at least tworemovable battery packs. The at least two battery packs may be connectedto each other in series. Each battery pack may have a rated DC voltagethat is approximately half of the rated AC voltage. The motor may be auniversal motor. The control circuit may be configured to operate theuniversal motor at a constant no load speed. The control circuit isconfigured to operate the universal motor at a variable no load speedbased upon a user input. The motor may include a brushless motor.

In another aspect, a power tool includes a power supply interface, amotor, and a motor control circuit. The a power supply interface isconfigured to receive AC power from an AC mains power supply having arated AC voltage and to receive DC power from a DC power supplycomprising one or more battery packs together having a rated DC voltagethat is different from the rated AC voltage. The motor has a ratedvoltage that corresponds to one of the rated AC voltage and the rated DCvoltage. The motor is operable using both the AC power from the AC powersupply and the DC power from the DC power supply. The motor controlcircuit is configured to enable operation of the motor using one of theAC power and the DC power, such that the motor substantially the sameoutput speed performance when operating using the AC power supply andthe DC power supply.

Implementations of this aspect may include one or more of the followingfeatures. The rated DC voltage may be less than the rated AC voltage.The rated AC voltage may be approximately 100 volts to 120 volts and therated DC voltage may be less than 100 volts. The rated DC voltage may beapproximately 51 volts to 60 volts. The rated AC voltage may be lessthan the rated DC voltage. The one or more battery packs may include twobattery packs connected to one another in series, wherein each batterypack has a rated voltage that is approximately half of the rated ACvoltage. The motor may be a universal motor. The control circuit mayoperate the universal motor at a constant no load speed. The controlcircuit may operate the universal motor at a variable no load speedbased upon a user input. The control circuit may optimize a range ofpulse-width-modulation according to the rated voltages of the AC powersupply and the DC power supply so that the motor substantially the sameoutput speed performance when operating using the AC power supply andthe DC power supply. The motor may be a brushless motor. The controlcircuit may use at least one of cycle-by-cycle current limiting,conduction band control, and advance angle control such that the motorsubstantially the same output speed performance when operating using theAC power supply and the DC power supply.

In another aspect, a power tool includes a means for receiving AC powerfrom an AC mains power supply having a rated AC voltage and a means forreceiving DC power from a DC power supply comprising one or more batterypacks together having a rated DC voltage that is different from therated AC voltage. The power tool also has a motor having a rated voltagethat corresponds to the higher of the rated AC voltage and the rated DCvoltage. The motor is operable using both the AC power from the AC powersupply and the DC power from the DC power supply. The power tool alsohas means for operating the motor using one of the AC power and the DCpower, such that the motor substantially the same output speedperformance when operating using the AC power supply and the DC powersupply.

Implementations of this aspect may include one or more of the followingfeatures. The rated DC voltage may be less than the rated AC voltage.The rated AC voltage may be approximately 100 volts to 120 volts and therated DC voltage may be less than 100 volts. The rated DC voltage may beapproximately 51 volts to 60 volts. The rated AC voltage may be lessthan the rated DC voltage. The one or more battery packs may include twobattery packs connected to one another in series, wherein each batterypack has a rated voltage that is approximately half of the rated ACvoltage. The motor may be a universal motor. The means for operating themotor may operate the universal motor at a constant no load speed. Themeans for operating the motor may operate the universal motor at avariable no load speed based upon a user input. The means for operatingthe motor may optimize a range of pulse-width-modulation according tothe rated voltages of the AC power supply and the DC power supply sothat the motor substantially the same output speed performance whenoperating using the AC power supply and the DC power supply. The motormay be a brushless motor. The means for operating the motor may use atleast one of cycle-by-cycle current limiting, conduction band control,and advance angle control such that the motor substantially the sameoutput speed performance when operating using the AC power supply andthe DC power supply.

In another aspect, a power tool system includes a first power toolhaving a first power tool rated voltage, a second power tool having asecond power tool rated voltage that is different from the first powertool rated voltage, and a first battery pack coupleable to the firstpower tool and to the second power tool. The first battery pack isswitchable between a first configuration having a first battery packrated voltage that corresponds to the first power tool rated voltagesuch that the first battery pack enables operation of the first powertool, and a second configuration having a convertible battery pack ratedvoltage that corresponds to the second power tool rated voltage suchthat the battery pack enables operation of the second power tool.

Implementations of this aspect may include one or more of the followingfeatures. The system may include a second removable battery pack havingthe first battery pack rated voltage and configured to be coupled to thefirst power tool to enable operation of the first power tool, but thatdoes not enable operation of the second power tool. The second powertool rated voltage may be greater than the first power tool ratedvoltage. The first power tool rated voltage may be a whole numbermultiple of the second power tool rated voltage. The first power toolrated voltage may be approximately 17 volts to 20 volts and the secondpower tool rated voltage range may be approximately 51 volts to 60volts. The first power tool may have been on sale prior to May 18, 2014,and the second power tool may not have been on sale prior to May 18,2014. The first power tool may be a DC-only power tool and the secondpower tool may be a DC-only power tool or an AC/DC power tool. Thesecond power may be alternatively coupleable to an AC power supplyhaving a rated voltage that corresponds to a voltage rating of an ACmains power supply to enable operation of the second power tool usingeither the convertible battery pack or the AC power supply.

According to another aspect of the invention, a power tool is providedcomprising: a housing; an electric universal motor having a positiveterminal, a negative terminal, and a commutator engaging a pair ofbrushes coupled to the positive and the negative terminals, the motorbeing configured to operate within an operating voltage range ofapproximately 90V to 132V; a power supply interface arranged to receiveat least one of AC power from an AC power supply having a first nominalvoltage or DC power from a DC power supply having a second nominalvoltage, the DC power supply comprising at least one removable batterypack coupled to the power supply interface, the power supply interfaceconfigured to output the AC power via an AC power line and the DC powervia a DC power line, wherein the first and second nominal voltages fallapproximately within the operating voltage range of the motor; and amotor control circuit configured to supply electric power from one ofthe AC power line or the DC power line via a common node to the motorsuch that the brushes are electrically coupled to one of the AC or DCpower supplies.

In an embodiment, the motor control circuit comprises an ON/OFF switcharranged between the common node of the AC and DC power lines and themotor.

In an embodiment, the motor control circuit comprises a control unitcoupled to a power switch arranged on the DC power line. In anembodiment, the control unit is configured to monitor a fault conditionassociated with the DC power supply and turn the power switch off to cutoff a supply of power from the DC power supply to the motor.

In an embodiment, the power tool further comprises a power supplyswitching unit arranged to isolate the AC power line and the DC powerline. In an embodiment, the power supply switching unit comprises arelay switch arranged on the DC power line and activated by a coilcoupled to the AC power line. In an embodiment, the power supplyswitching unit comprises at least one double-pole double-throw switcharranged between the common node of the AC and DC power lines and thepower supply interface. In an embodiment, the power supply switchingunit comprises at least one single-pole double-throw switch having anoutput terminal coupled to the common node of the AC and DC power lines.

In an embodiment, the DC power supply comprises a high rated voltagebattery pack.

In an embodiment, the DC power supply comprises at least twomedium-rated voltage battery packs and the power supply interface isconfigured to connect two or more of the at least two battery packs inseries.

According to another aspect of the invention, the power tool describedabove is a variable-speed tool, as described herein.

In an embodiment, the power tool further comprises: a DC switch circuitarranged between the DC power line and the motor; an AC switch arrangedbetween the AC power line and the motor; and a control unit configuredto control a switching operation of the DC switch circuit or the ACswitch to control a speed of the motor enabling variable speed operationof the motor at constant torque.

In an embodiment, the DC switch circuit comprises one or morecontrollable semiconductor switches configured in at least one of achopper circuit, a half-bridge circuit, or a full-bridge circuit, andthe control unit is configured to control a pulse-width modulation (PWM)duty cycle of the one or more semiconductor switches according to adesired speed of the motor.

In an embodiment, the AC switch comprises a phase controlled switchcomprising at least one of a triac, a thyristor, or a SCR switch, andthe control unit is configured to control a phase of the AC switchaccording to a desired speed of the motor.

In an embodiment, the control unit is configured to sense current on oneof the AC power line or the DC power line to set a mode of operation toone of an AC mode of operation or a DC mode of operation, and controlthe switching operation of one or the other of the DC switch circuit orthe AC switch based on the mode of operation.

In an alternative embodiment, the power tool further comprises: a powerswitching unit comprising a diode bridge and a controllablesemiconductor switch nested within the diode bridge, wherein the AC andDC power lines of the power supply interface are jointly coupled to afirst node of the diode bridge and the motor is coupled to a second nodeof the diode bridge; and a control unit configured to control aswitching operation of the semiconductor switch to control a speed ofthe motor enabling variable speed operation of the motor at constanttorque.

In an embodiment, the control unit is configured to sense current on oneof the AC power line or the DC power line to set a mode of operation toone of an AC mode of operation or a DC mode of operation, and controlthe switching operation of the semiconductor switch according to themode of operation.

In an embodiment, in the DC mode of operation, the control unit isconfigured to set a pulse-width modulation (PWM) duty cycle according toa desired speed of the motor and turn the semiconductor switch on andoff periodically in accordance with the PWM duty cycle.

In an embodiment, in the AC mode of operation, the control unit isconfigured to set a conduction band according to a desired speed of themotor and, within each AC line half-cycle, turn the semiconductor switchON at approximately the beginning of the conduction band and turn thesemiconductor switch OFF at approximately a zero crossing of the ACpower line.

In an embodiment, the power tool further comprises a secondsemiconductor switch and a freewheel diode disposed in series with themotor to allow a current path for a motor current during an off-cycle ofthe semiconductor switch in the DC mode of operation.

In an embodiment, the semiconductor switch comprises one of a fieldeffect transistor (FET) or an insulated gate bipolar transistor (IGBT).

In an embodiment, the diode bridge is arranged to rectify the AC powerline through the semiconductor switch, but not through the motor.

In an embodiment, the semiconductor switching unit is arranged betweenthe common node of the AC and DC power lines.

According to another aspect of the invention, a power tool is providedcomprising: a housing; a universal motor having a positive terminal, anegative terminal, and a commutator engaging a pair of brushes coupledto the positive and the negative terminals, the motor being configuredto operate within an operating voltage range; a power supply interfacearranged to receive at least one of AC power from an AC power supplyhaving a first nominal voltage or DC power from a DC power supply havinga second nominal voltage, the DC power supply comprising at least oneremovable battery pack coupled to the power supply interface, the powersupply interface configured to output the AC power via an AC power lineand the DC power via a DC power line, wherein the second nominal voltagefalls approximately within the operating voltage range of the motor, butthe first nominal voltage is substantially higher than the operatingvoltage range of the motor; and a motor control circuit configured tosupply electric power from one of the AC power line or the DC power linevia a common node to the motor such that the brushes are electricallycoupled to one of the AC or DC power supplies, the motor control circuitbeing configured to reduce a supply of power from the AC power line tothe motor to a level corresponding to the operating voltage of theoperating voltage range of the motor.

In an embodiment, the motor control circuit comprises an AC switchdisposed in series with the AC power line, and a control unit configuredto control a phase of the AC power line via the AC switch and set afixed conduction band of the AC switch to reduce an average voltageamount on the AC line to a level corresponding to the operating voltagerange of the motor to a level corresponding to the operating voltagerange of the motor.

In an embodiment, the motor control circuit comprises an ON/OFF switcharranged between the common node of the AC and DC power lines and themotor.

In an embodiment, the motor control circuit comprises a control unitcoupled to a power switch arranged on the DC power line. In anembodiment, the control unit is configured to monitor a fault conditionassociated with the DC power supply and turn the power switch off to cutoff a supply of power from the DC power supply to the motor.

In an embodiment, the power tool further comprises a power supplyswitching unit arranged to isolate the AC power line and the DC powerline. In an embodiment, the power supply switching unit comprises arelay switch arranged on the DC power line and activated by a coilcoupled to the AC power line. In an embodiment, the power supplyswitching unit comprises at least one double-pole double-throw switcharranged between the common node of the AC and DC power lines and thepower supply interface. In an embodiment, the power supply switchingunit comprises at least one single-pole double-throw switch having anoutput terminal coupled to the common node of the AC and DC power lines.

In an embodiment, the DC power supply comprises a high rated voltagebattery pack.

In an embodiment, the DC power supply comprises at least twomedium-rated voltage battery packs and the power supply interface isconfigured to connect two or more of the at least two battery packs inseries. In an embodiment, the operating voltage range of the motor isapproximately within a range of 100V to 120V encompassing the secondnominal voltage, and the first nominal voltage is in the range of 220VAC to 240 VAC. In an embodiment, the control unit is configured to setthe fixed conduction band of the AC switch to a value within the rangeof 100 to 140 degrees.

In an embodiment, the operating voltage range of the motor isapproximately within a range of 60V to 90V encompassing the secondnominal voltage, and the first nominal voltage is in the range of 100VAC to 120 VAC. In an embodiment, the control unit is configured to setthe fixed conduction band of the AC switch to a value within the rangeof 70 to 110 degrees.

In an embodiment, the control unit is configured to operate the tool atconstant speed at the fixed conduction band.

In an embodiment, the AC switch includes a phase controlled switchcomprising one of a triac, a thyristor, or a SCR switch, and thecontroller is configured to control a phase of the AC switch accordingto a desired speed of the motor.

According to another aspect of the invention, the power tool describedabove is a variable-speed power tool, as described herein.

According to an embodiment, the motor control circuit further comprisinga DC switch circuit arranged between the DC power line and the motor,wherein the control unit is configured to control a switching operationof the DC switch circuit or the AC switch to control a speed of themotor enabling variable speed operation of the motor at constant load.

According to an embodiment, the DC switch circuit comprises one or morecontrollable semiconductor switches configured in at least one of achopper circuit, a half-bridge circuit, or a full-bridge circuit, andthe control unit is configured to control a pulse-width modulation (PWM)duty cycle of the one or more semiconductor switches according to adesired speed of the motor.

According to an embodiment, the control unit is configured to vary aconduction angle of the AC switch from zero up to the fixed conductionband according to a desired speed of the motor.

According to an embodiment, the control unit is configured to sensecurrent on one of the AC power line or the DC power line to set a modeof operation to one of an AC mode of operation or a DC mode ofoperation, and control the switching operation of one or the other ofthe DC switch circuit or the AC switch based on the mode of operation.

According to an embodiment, the motor control circuit comprises: a powerswitching unit including a diode bridge and a controllable semiconductorswitch nested within the diode bridge, wherein the AC and DC power linesof the power supply interface are jointly coupled to a first node of thediode bridge and the motor is coupled to a second node of the diodebridge; and a control unit configured to control a switching operationof the semiconductor switch to control a speed of the motor enablingvariable speed operation of the motor at constant load, wherein thecontrol unit is configured to control a phase of the AC power line viathe semiconductor switch.

In an embodiment, the control unit is configured to sense current on oneof the AC power line or the DC power line to set a mode of operation toone of an AC mode of operation or a DC mode of operation, and controlthe switching operation of the semiconductor switch in one of an AC modeor a DC mode of operation according to the mode of operation.

In an embodiment, in the DC mode of operation, the control unit isconfigured to set a pulse-width modulation (PWM) duty cycle according toa desired speed of the motor and turn the semiconductor switch on andoff periodically in accordance with the PWM duty cycle.

In an embodiment, in the AC mode of operation, the control unit isconfigured to set a maximum conduction band corresponding to theoperating voltage range of the motor.

In an embodiment, the control unit is configured to set a conductionband according to a desired speed of the motor from zero up to themaximum conduction band and in proportion thereto, and within each ACline half-cycle, turn the semiconductor switch ON at approximately thebeginning of the conduction band and turn the semiconductor switch OFFat approximately a zero crossing of the AC power line.

In an embodiment, the operating voltage range of the motor isapproximately within a range of 100V to 120V encompassing the secondnominal voltage, and the first nominal voltage is in the range of 220VAC to 240 VAC. In an embodiment, the control unit is configured to setthe maximum conduction band to a value within the range of 100 to 140degrees.

In an embodiment, the operating voltage range of the motor isapproximately within a range of 60V to 100V encompassing the secondnominal voltage, and the first nominal voltage is in the range of 100VAC to 120 VAC. In an embodiment, the control unit is configured to setthe maximum conduction band of the AC switch to a value within the rangeof 70 to 110 degrees.

In an embodiment, the diode bridge is arranged to rectify the AC powerline through the semiconductor switch, but not through the motor.

In an embodiment, the motor control circuit further comprising a secondsemiconductor switch and a freewheel diode disposed in series with themotor to allow a current path for a motor current during an off-cycle ofthe semiconductor switch in the DC mode of operation.

In an embodiment, the semiconductor switch comprises one of a fieldeffect transistor (FET) or an insulated gate bipolar transistor (IGBT).

According to another aspect of the invention, a power tool is providedcomprising: a housing; an electric universal motor having a positiveterminal, a negative terminal, and a commutator engaging a pair ofbrushes coupled to the positive and the negative terminals; a powersupply interface arranged to receive at least one of AC power from an ACpower supply or DC power from a DC power supply, and to output the ACpower via an AC power line and the DC power via a DC power line; a powerswitching unit comprising a diode bridge and a controllablesemiconductor switch nested within the diode bridge, wherein the AC andDC power lines of the power supply interface are jointly coupled to afirst node of the diode bridge and the motor is coupled to a second nodeof the diode bridge; and a control unit configured to control aswitching operation of the semiconductor switch to control a speed ofthe motor enabling variable speed operation of the motor at constanttorque.

In an embodiment, the control unit is configured to sense current on oneof the AC power line or the DC power line to set a mode of operation toone of an AC mode of operation or a DC mode of operation, and controlthe switching operation of the semiconductor switch according to themode of operation.

In an embodiment, in the DC mode of operation, the control unit isconfigured to set a pulse-width modulation (PWM) duty cycle according toa desired speed of the motor and turn the semiconductor switch on andoff periodically in accordance with the PWM duty cycle.

In an embodiment, in the AC mode of operation, the control unit isconfigured to set a conduction band according to a desired speed of themotor and, within each AC line half-cycle, turn the semiconductor switchON at approximately the beginning of the conduction band and turn thesemiconductor switch OFF at approximately a zero crossing of the ACpower line.

In an embodiment, the power tool further comprises a secondsemiconductor switch and a freewheel diode disposed in series with themotor to allow a current path for a motor current during an off-cycle ofthe semiconductor switch in the DC mode of operation.

In an embodiment, the semiconductor switch comprises one of a fieldeffect transistor (FET) or an insulated gate bipolar transistor (IGBT).

In an embodiment, the diode bridge is arranged to rectify the AC powerline through the semiconductor switch, but not through the motor.

In an embodiment, the power switching unit is arranged between thecommon node of the AC and DC power lines.

According to another aspect of the invention, a power tool is providedcomprising: a housing; an electric direct-current (DC) motor having apositive terminal, a negative terminal, and a commutator engaging a pairof brushes coupled to the positive and the negative terminals, the motorbeing configured to operate within an operating voltage range within arange of approximately 90V to 132V; a power supply interface arranged toreceive at least one of AC power from an AC power supply having a firstnominal voltage or DC power from a DC power supply having a secondnominal voltage, the DC power supply comprising at least one removablebattery pack coupled to the power supply interface, the power supplyinterface configured to output the AC power via an AC power line and theDC power via a DC power line, wherein the first and second nominalvoltages fall approximately within the operating voltage range of themotor; and a motor control circuit including a rectifier circuitconfigured to rectify an alternating signal to a rectified signal on theAC power line, the motor control circuit being configured to supplyelectric power from one of the AC power line or the DC power line via acommon node to the motor such that the brushes are electrically coupledto one of the AC or DC power supplies.

In an embodiment, the rectifier circuit includes a full-wave diodebridge rectifier.

In an embodiment, the motor control circuit comprises an ON/OFF switcharranged between the common node of the AC and DC power lines and themotor.

In an embodiment, the motor control circuit comprises a control unitcoupled to a power switch arranged on the DC power line. In anembodiment, the control unit is configured to monitor a fault conditionassociated with the DC power supply and turn the power switch off to cutoff a supply of power from the DC power supply to the motor.

In an embodiment, the power tool further comprises a power supplyswitching unit arranged to isolate the AC power line and the DC powerline. In an embodiment, the power supply switching unit comprises arelay switch arranged on the DC power line and activated by a coilcoupled to the AC power line. In an embodiment, the power supplyswitching unit comprises at least one double-pole double-throw switcharranged between the common node of the AC and DC power lines and thepower supply interface. In an embodiment, the power supply switchingunit comprises at least one single-pole double-throw switch having anoutput terminal coupled to the common node of the AC and DC power lines.

In an embodiment, the DC power supply comprises a high rated voltagebattery pack.

In an embodiment, the DC power supply comprises at least twomedium-rated voltage battery packs and the power supply interface isconfigured to connect two or more of the at least two battery packs inseries.

According to another aspect of the invention, the power tool describedabove is a variable-speed tool, as described herein.

In an embodiment, the power tool further comprises: a switching circuitarranged between the common node of the AC and DC power lines and themotor; and a control unit configured to control a switching operation ofthe switching circuit to control a speed of the motor enabling variablespeed operation of the motor at constant torque.

In an embodiment, the switching circuit comprises one or morecontrollable semiconductor switches configured in at least one of achopper circuit, a half-bridge circuit, or a full-bridge circuit, andthe control unit is configured to control a pulse-width modulation (PWM)duty cycle of the one or more semiconductor switches according to adesired speed of the motor.

In an embodiment, the motor is a permanent magnet DC motor.

According to another aspect of the invention, a power tool is providedcomprising: a housing; an electric direct-current (DC) motor having apositive terminal, a negative terminal, and a commutator engaging a pairof brushes coupled to the positive and the negative terminals, the motorbeing configured to operate within an operating voltage range; a powersupply interface arranged to receive at least one of AC power from an ACpower supply having a first nominal voltage or DC power from a DC powersupply having a second nominal voltage, the DC power supply comprisingat least one removable battery pack coupled to the power supplyinterface, the power supply interface configured to output the AC powervia an AC power line and the DC power via a DC power line, wherein thesecond nominal voltage falls approximately within the operating voltagerange of the motor, but the first nominal voltage is substantiallyhigher than the operating voltage range of the motor; and a motorcontrol circuit including a rectifier circuit configured to rectify analternating signal to a rectified signal on the AC power line, the motorcontrol circuit being configured to supply electric power from one ofthe AC power line or the DC power line via a common node to the motorsuch that the brushes are electrically coupled to one of the AC or DCpower supplies, the motor control circuit being configured to reduce asupply of power from the AC power line to the motor to a levelcorresponding to the operating voltage range of the motor.

In an embodiment, the rectifier circuit includes a half-wave diodebridge circuit arranged to reduce an average voltage amount on the ACpower line by approximately half.

In an embodiment, the motor control circuit comprises a power switcharranged between the common node of the AC and DC power lines and acontrol unit configured to control a pulse-width modulation (PWM) of thepower switch, wherein the control unit is configured to set apulse-width modulation (PWM) duty cycle of the power switch to a fixedvalue less than 100% to reduce an average voltage amount on the AC lineto a level corresponding to the operating voltage range of the motor. Inan embodiment, the power switch comprises one of a field effecttransistor (FET) or an insulated gate bipolar transistor (IGBT).

In an embodiment, the motor control circuit comprises an AC switchdisposed in series with the AC power line between the power supplyinterface and the rectifier circuit and a control unit configured tocontrol a phase of the AC power line via the AC switch and set a fixedconduction band of the AC switch to reduce an average voltage amount onthe AC power line to a level corresponding to the operating voltagerange of the motor.

In an embodiment, the AC switch includes a phase controlled switchcomprising one of a triac, a thyristor, or a SCR switch, and thecontroller is configured to control a phase of the AC switch accordingto a desired speed of the motor.

In an embodiment, the motor control circuit comprises an ON/OFF switcharranged between the common node of the AC and DC power lines and themotor.

In an embodiment, the motor control circuit comprises a control unitcoupled to a power switch arranged on the DC power line. In anembodiment, the control unit is configured to monitor a fault conditionassociated with the DC power supply and turn the power switch off to cutoff a supply of power from the DC power supply to the motor.

In an embodiment, the power tool further comprises a power supplyswitching unit arranged to isolate the AC power line and the DC powerline. In an embodiment, the power supply switching unit comprises arelay switch arranged on the DC power line and activated by a coilcoupled to the AC power line. In an embodiment, the power supplyswitching unit comprises at least one double-pole double-throw switcharranged between the common node of the AC and DC power lines and thepower supply interface. In an embodiment, the power supply switchingunit comprises at least one single-pole double-throw switch having anoutput terminal coupled to the common node of the AC and DC power lines.

In an embodiment, the DC power supply comprises a high rated voltagebattery pack.

In an embodiment, the DC power supply comprises at least twomedium-rated voltage battery packs and the power supply interface isconfigured to connect two or more of the at least two battery packs inseries. In another embodiment, the operating voltage range of the motoris approximately within a range of 100V to 120V encompassing the secondnominal voltage, and the first nominal voltage is in the range of 220VAC to 240 VAC. In an embodiment, the control unit is configured to setthe fixed conduction band of the AC switch to a value within the rangeof 100 to 140 degrees.

In an embodiment, the operating voltage range of the motor isapproximately within a range of 60V to 90V encompassing the secondnominal voltage, and the first nominal voltage is in the range of 100VAC to 120 VAC. In an embodiment, the control unit is configured to setthe fixed conduction band of the AC switch to a value within the rangeof 70 to 110 degrees.

In an embodiment, the control unit is configured to operate the tool atconstant speed at the fixed conduction band.

According to another aspect of the invention, the power tool describedabove is a variable-speed tool, as described herein.

In an embodiment, the power tool further comprises: a switching circuitarranged between the common node of the AC and DC power lines and themotor; and a control unit configured to control a pulse-width modulation(PWM) switching operation of the switching circuit to control a speed ofthe motor enabling variable speed operation of the motor at constanttorque.

In an embodiment, the switching circuit comprises one or morecontrollable semiconductor switches configured in at least one of achopper circuit, a half-bridge circuit, or a full-bridge circuit, andthe control unit is configured to control a pulse-width modulation (PWM)duty cycle of the one or more semiconductor switches according to adesired speed of the motor.

According to an embodiment, the control unit is configured to sensecurrent on one of the AC power line or the DC power line to set a modeof operation to one of an AC mode of operation or a DC mode ofoperation.

In an embodiment, the controller is configured to reduce a supply ofpower through the switching circuit to a level corresponding to theoperating voltage range of the motor in the AC mode of operation.

In an embodiment, the control unit is configured to control theswitching operation of the switching circuit within a first duty cyclerange in the DC mode of operation, and control the switching operationof the switching circuit within a second duty cycle range in the AC modeof operation, wherein the second duty cycle range is smaller than thefirst duty cycle range.

In an embodiment, the control unit is configured to control theswitching operation of the switching circuit at zero to 100% duty cyclein the DC mode of operation, and control the switching operation of theswitching circuit from zero to a threshold value less than 100% in theAC mode of operation.

According to another aspect of the invention, a power tool is providedcomprising: a housing; a brushless direct current (BLDC) motor includinga rotor and a stator having at least three stator windings correspondingto at least three phases of the motor, the rotor being moveable by thestator when the stator windings are appropriately energized within thecorresponding phases, each phase being characterized by a correspondingvoltage waveform energizing the corresponding stator winding, the motorbeing configured to operate within an operating voltage range; a powersupply interface arranged to receive at least one of AC power from an ACpower supply having a first nominal voltage or DC power from a DC powersupply having a second nominal voltage, the DC power supply comprisingat least one removable battery pack coupled to the power supplyinterface, the power supply interface configured to output the AC powervia an AC power line and the DC power via a DC power line; and a motorcontrol circuit configured to receive the AC power line and the DC powerline and supply electric power to the motor at a level corresponding tothe operating voltage range of the motor, the motor control circuithaving a rectifier circuit configured to rectify an alternating signalon the AC power line to a rectified voltage signal on a DC bus line, anda power switch circuit configured to regulate a supply of electric powerfrom the DC bus line to the motor.

In an embodiment, the rectifier circuit comprises a diode bridge. In anembodiment, the rectifier circuit further comprises a link capacitorarranged in parallel to the diode bridge on the DC bus line. In anembodiment, the diode bridge comprises a full-wave bridge. In analternative embodiment, the diode bridge comprises a half-wave bridge.

In an embodiment, the DC power line is connected directly to a node onthe DC bus line bypassing the rectifier circuit. In an alternativeembodiment, the DC power line and the AC power line are jointly coupledto an input node of the rectifier circuit.

In an embodiment, the power tool further comprises a power supplyswitching unit arranged to isolate the AC power line and the DC powerline. In an embodiment, the switching unit comprises a relay switcharranged on the DC power line and activated by a coil coupled to the ACpower line. In an embodiment, the power supply switching unit comprisesat least one single-pole double-throw switch having input terminalscoupled to the AC and DC power lines and an output terminal coupled toan input node of the rectifier circuit. In an embodiment, the powersupply switching unit comprises at least one double-pole double-throwswitch having input terminals coupled to the AC and DC power lines, afirst output terminal coupled to the input node of the rectifiercircuit, and a second output terminal coupled directly to a node on theDC bus line bypassing the rectifier circuit.

In an embodiment, the motor control circuit further comprises acontroller arranged to control a switching operation of the power switchcircuit. In an embodiment, the controller is a programmable deviceincluding a microcontroller, a microprocessor, a computer processor, asignal processor. Alternatively, the controller is an integrated circuitconfigured and customized to control a switching operation of the powerswitch unit. In an embodiment, the control unit is further configured tomonitor a fault condition associated with the power tool or the DC powersupply and deactivate the power switch circuit to cut off a supply ofpower to the motor. In an embodiment, the control unit is configured tosense current on one of the AC power line or the DC power line to set amode of operation to one of an AC mode of operation or a DC mode ofoperation, and control the switching operation of the power switchcircuit based on the mode of operation. In an alternative embodiment,the control unit is configured to control the switching operation of thepower switch circuit irrespective of an AC or DC mode of operation.

In an embodiment, the power switch circuit comprises a plurality ofpower switches including three pairs of high-side and low-side powerswitches configured as a three-phase bridge circuit coupled to thephases of the motor.

In an embodiment, the motor control circuit further comprises a gatedriver circuit coupled to the controller and the power switch circuit,and configured to drive gates of the plurality of power switches basedon one or more drive signals from the controller.

In an embodiment, the motor control circuit further comprises a powersupply regulator including at least one voltage regulator configured tooutput a voltage signal to power at least one of the gate driver circuitor the controller.

In an embodiment, the motor control circuit further comprises an ON/OFFswitch coupled to at least one of an ON/OFF actuator or a trigger switchand arranged to cut off a supply of power from the power supplyregulator and the gate driver circuit.

In an embodiment, the power tool further comprises a plurality ofposition sensors disposed at close proximity to the rotor to providerotational position signals of the rotor to the control unit. In anembodiment, the controller is configured to control the switchingoperation of the power switch circuit based on the position signals toappropriately energize the stator windings within the correspondingphases.

According to an embodiment, within each phase of the motor, thecontroller is configured to activate a drive signal for a correspondingone of the plurality of power switches within a conduction bandcorresponding to the phase of the motor.

In an embodiment, the controller is configured to set a pulse-widthmodulation (PWM) duty cycle according to a desired speed of the motorand control the drive signal to turn the corresponding one of theplurality of power switches on and off periodically within theconduction band in accordance with the PWM duty cycle to enable variablespeed operation of the motor at constant load.

According to an aspect of the invention, the first and second nominalvoltages both fall approximately within the operating voltage range ofthe motor.

In an embodiment, the operating voltage range of the motor isapproximately within a range of 90V to 132V encompassing the secondnominal voltage, and the first nominal voltage is in the range ofapproximately 100 VAC to 120 VAC. In an embodiment, the DC power supplycomprises a high-rated voltage battery pack. In an embodiment, the DCpower supply comprises at least two medium-rated voltage battery packsand the power supply interface is configured to connect two or more ofthe at least two battery packs in series.

In an embodiment, the link capacitor has a capacitance value optimizedto provide an average voltage of approximately less than or equal to110V on the DC bus line when the power tool is powered by the AC powersupply, where the first nominal voltage is approximately 120 VAC. In anembodiment, the link capacitor has a capacitance value of less than orequal to approximately 50 μF.

In an embodiment, the link capacitor has a capacitance value optimizedto provide an average voltage of approximately 120V on the DC bus linewhen the power tool is powered by the AC power supply, where the firstnominal voltage is approximately 120 VAC. In an embodiment, the linkcapacitor has a capacitance value of less than or equal to approximately200 to 600 μF. In an embodiment, the DC power supply has a nominalvoltage of approximately 120 VDC.

According to an aspect of the invention, at least one of first andsecond nominal voltages does not approximately correspond to theoperating voltage range of the motor.

In an embodiment, the motor control circuit is configured to optimize asupply of power from at least one of the AC power line or the DC powerline to the motor at a level corresponding to the operating voltagerange of the motor.

In an embodiment, the controller is configured to set a mode ofoperation to one of an AC mode of operation or a DC mode of operation,and control the switching operation of the power switch circuit based onthe mode of operation. In an embodiment, the controller is configured tosense current on one of the AC power line or the DC power line to setthe mode of operation. In an embodiment, the controller is configured toreceive a signal from the power supply interface indicative of the modeof operation.

In an embodiment, the operating voltage range of the motor encompassesthe first nominal voltage, but not the second nominal voltage. In anembodiment, the operating voltage range of the motor is approximatelywithin a range of 100V to 120V encompassing the first nominal voltage,and the second nominal voltage is in a range of approximately 60 VDC to100 VDC. In an embodiment, the controller may be configured to boost aneffective supply of power to the motor in the DC mode of operation tocorrespond to the operating voltage range of the motor.

In an embodiment, the operating voltage range of the motor encompassesthe second nominal voltage, but not the first nominal voltage. In anembodiment, the operating voltage range of the motor is approximatelywithin a range of 60V to 100V encompassing the second nominal voltage,and the first nominal voltage is in a range of approximately 100 VAC to120 VAC. In an embodiment, the controller may be configured to reduce aneffective supply of power to the motor in the AC mode of operation tocorrespond to the operating voltage range of the motor.

In an embodiment, the operating voltage range of the motor encompassesneither the first nominal voltage nor the first nominal voltage. In anembodiment, the motor control circuit is configured to optimize a supplyof power from both the AC power line and the DC power line to the motorat a level corresponding to the operating voltage range of the motor.

In an embodiment, the operating voltage range of the motor isapproximately within a range of 150V to 170V, the first nominal voltageis in a range of approximately 100 VAC to 120 VAC, and the secondnominal voltage is in a range of approximately 90 VDC to 120 VDC. In anembodiment, the controller may be configured to boost an effectivesupply of power to the motor in both the AC mode of operation and the DCmode of operation to correspond to the operating voltage range of themotor.

In an embodiment, the operating voltage range of the motor isapproximately within a range of 150V to 170V, the first nominal voltageis in a range of approximately 220 VAC to 240 VAC, and the secondnominal voltage is in a range of approximately 90 VDC to 120 VDC. In anembodiment, the controller may be configured to boost an effectivesupply of power to the motor in the DC mode of operation, but reduce aneffective supply of power to the motor in the AC mode of operation, tocorrespond to the operating voltage range of the motor.

In an embodiment, the controller is configured to control the switchingoperation of the power switch circuit via one or more drive signals at afixed pulse-width modulation (PWM) duty cycle, the controller settingthe fixed PWM duty cycle to a first value in relation to the firstnominal voltage when powered by the AC power supply and to a secondvalue different from the first value and in relation to the secondnominal voltage when powered by the DC power supply.

In an embodiment, the controller is configured to control the switchingoperation of the power switch circuit via one or more drive signals at afixed pulse-width modulation (PWM) duty cycle of less than 100% in theAC mode of operation to reduce an effective supply of power to the motorin the AC mode of operation to correspond to the operating voltage rangeof the motor.

In an embodiment, the controller is configured to control the switchingoperation of the power switch circuit via one or more drive signals at apulse-width modulation (PWM) duty cycle up to a threshold value, thecontroller setting the threshold value to a first value in relation tothe first nominal voltage when powered by the AC power supply and to asecond value different from the first value and in relation to thesecond nominal voltage when powered by the DC power supply.

In an embodiment, the controller is configured to control the switchingoperation of the power switch circuit within a first duty cycle range inthe DC mode of operation, and control the switching operation of thepower switch circuit within a second duty cycle range in the AC mode ofoperation, wherein the second PWM duty cycle range is smaller than thefirst duty cycle range, in order to reduce an effective supply of powerto the motor in the AC mode of operation to correspond to the operatingvoltage range of the motor.

In an embodiment, the controller is configured to control the switchingoperation of the power switch circuit at zero to 100% duty cycle in theDC mode of operation, and control the switching operation of the powerswitch circuit from zero to a threshold value less than 100% in the ACmode of operation, in order to reduce an effective supply of power tothe motor in the AC mode of operation to correspond to the operatingvoltage range of the motor.

In an embodiment, the controller is configured to receive a measure ofinstantaneous current on the DC bus line and enforce a current limit oncurrent through the power switch circuit by comparing instantaneouscurrent measures to the current limit and, in response to aninstantaneous current measure exceeding the current limit, turning offthe plurality of power switches for a remainder of a present timeinterval to interrupt current flowing to the electric motor, whereduration of each time interval is fixed as a function of the givenfrequency at which the electric motor is controlled by the controller.

In an embodiment, the controller turns on select power switches at endof the present time interval and thereby resumes current flow to themotor.

In an embodiment, the duration of each time interval is approximatelyten times an inverse of the given frequency at which the motor iscontrolled by the controller. In an embodiment, the duration of eachtime interval is on the order to 100 microseconds.

In an embodiment, duration of the each time interval corresponds to aperiod of pulse-width modulation (PWM) cycle.

In an embodiment, the controller is configured to receive a measure ofcurrent on the DC bus line and enforce a current limit on currentthrough the power switch circuit by setting or adjusting a PWM dutycycle of the one or more drive signals. In an embodiment, the controlleris configured to monitor the current through the DC bus line and adjustthe PWM duty cycle if the current through the DC bus line exceeds thecurrent limit.

In an embodiment, the controller is configured to set the current limitaccording to a voltage rating of one of the AC or the DC power supplies.

In an embodiment, the controller is configured to set the current limitto a first threshold in the AC mode of operation and to a secondthreshold in the DC mode of operation, wherein the second threshold ishigher than the first threshold, in order to reduce an effective supplyof power to the motor in the AC mode of operation to correspond to theoperating voltage range of the motor.

According to an embodiment, the controller is configured to activate adrive signal within each phase of the motor for a corresponding one ofthe plurality of power switches within a conduction band (CB)corresponding to the phase of the motor. According to an embodiment, theCB is set to approximately 120 degrees.

In an embodiment, the controller is configured to shift the CB by anadvance angle (AA) such that the CB leads ahead of a backelectro-magnetic field (EMF) current of the motor. According to anembodiment, the AA is set to approximately 30 degrees.

In an embodiment, the controller is configured to set at least one ofthe CB or AA according to a voltage rating of one or more of the AC orDC power supplies. In an embodiment, the controller is configured to setat least one of the CB or AA to a first value in relation to the firstnominal voltage when powered by the AC power supply and to a secondvalue different from the first value and in relation to the secondnominal voltage when powered by the DC power supply.

In an embodiment, the controller is configured set to the CB to a firstCB value during the AC mode of operation and to a second CB valuegreater than the first CB value during the DC mode of operation. In anembodiment, the second CB value is determined so as to boost aneffective supply of power to the motor in the DC mode of operation tocorrespond to the operating voltage range of the motor. In anembodiment, first CB value is approximately 120 degrees and the secondCB value is greater than approximately 130 degrees.

In an embodiment, the controller is configured set to the AA to a firstAA value during the AC mode of operation and to a second AA valuegreater than the first AA value during the DC mode of operation. In anembodiment, the second AA value is determined so as to boost aneffective supply of power to the motor in the DC mode of operation tocorrespond to the operating voltage range of the motor. In anembodiment, first AA value is approximately 30 degrees and the second AAvalue is greater than approximately 35 degrees.

In an embodiment, the controller is configure to set the CB and AA intandem according to the voltage rating of the AC or DC power supplies.

In an embodiment, the controller is configured to set at least one ofthe CB or AA to a base value corresponding to a maximum speed of themotor at approximately no load, and gradually increase the at least oneof CB or AA from the base value to a threshold value in relation to anincrease in torque to yield a substantially linear speed-torque curve.In an embodiment, the controller is configured to maintain substantiallyconstant speed on the speed-torque curve. In an embodiment, the basevalue and the threshold value corresponds to a low torque range withinwhich the speed-torque curve is substantially linear. In an embodiment,the controller is configured to maintain the at least one of CB or AA atthe torque greater than the low torque range.

According to another aspect of the invention, a power tool is providedcomprising: a housing; a brushless direct current (BLDC) motor includinga rotor and a stator having at least three stator windings correspondingto at least three phases of the motor, the rotor being moveable by thestator when the stator windings are appropriately energized within thecorresponding phases, each phase being characterized by a correspondingvoltage waveform energizing the corresponding stator winding, the motorbeing configured to operate within an operating voltage range; and amotor control circuit configured to receive electric power from a firstpower supply having a first nominal voltage or a second power supplyhaving a second nominal voltage different from the first nominalvoltage, and to provide electric power to the motor at a levelcorresponding to the operating voltage range of the motor. In anembodiment, the first and second power supplies each comprise an ACpower supply or a DC power supply.

In an embodiment, at least one of first and second nominal voltages doesnot approximately correspond to, is different from, or is outside theoperating voltage range of the motor. In an embodiment, the motorcontrol circuit is configured to optimize a supply of power from atleast one of the first or second power supplies to the motor at a levelcorresponding to the operating voltage range of the motor.

In an embodiment, the operating voltage range of the motor encompassesthe first nominal voltage, but not the second nominal voltage. In anembodiment, the operating voltage range of the motor is approximatelywithin a range of 100V to 120V encompassing the first nominal voltage,and the second nominal voltage is in a range of approximately 60V to100V. In an embodiment, the controller may be configured to boost aneffective supply of power to the motor to correspond to the operatingvoltage range of the motor when powered by the second power supply.

In an embodiment, the operating voltage range of the motor encompassesthe second nominal voltage, but not the first nominal voltage. In anembodiment, the operating voltage range of the motor is approximatelywithin a range of 60V to 100V encompassing the second nominal voltage,and the first nominal voltage is in a range of approximately 100 VAC to120 VAC. In an embodiment, the controller may be configured to reduce aneffective supply of power to the motor to correspond to the operatingvoltage range of the motor when powered by the first power supply.

In an embodiment, the operating voltage range of the motor encompassesneither the first nominal voltage nor the first nominal voltage. In anembodiment, the motor control circuit is configured to optimize a supplyof power from both the first and the second power supplies to the motorat a level corresponding to the operating voltage range of the motor.

In an embodiment, at least one of the first or second power suppliescomprises an AC power supply and the motor control circuit comprises arectifier circuit including a diode bridge. In an embodiment, therectifier circuit further comprises a link capacitor arranged inparallel to the diode bridge on the DC bus line. In an embodiment, thediode bridge comprises a full-wave bridge. In an alternative embodiment,the diode bridge comprises a half-wave bridge.

In an embodiment, both the first and the second power supplies compriseDC power supplies having different nominal voltage levels.

In an embodiment, the motor control circuit further comprises acontroller arranged to control a switching operation of the power switchcircuit. In an embodiment, the controller is a programmable deviceincluding a microcontroller, a microprocessor, a computer processor, asignal processor. Alternatively, the controller is an integrated circuitconfigured and customized to control a switching operation of the powerswitch unit.

In an embodiment, the power switch circuit comprises a plurality ofpower switches including three pairs of high-side and low-side powerswitches configured as a three-phase bridge circuit coupled to thephases of the motor. In an embodiment, the motor control circuit furthercomprises a gate driver circuit coupled to the controller and the powerswitch circuit, and configured to drive gates of the plurality of powerswitches based on one or more drive signals from the controller. In anembodiment, the motor control circuit further comprises a power supplyregulator including at least one voltage regulator configured to outputa voltage signal to power at least one of the gate driver circuit or thecontroller. In an embodiment, the motor control circuit furthercomprises an ON/OFF switch coupled to at least one of an ON/OFF actuatoror a trigger switch and arranged to cut off a supply of power from thepower supply regulator and the gate driver circuit.

In an embodiment, the power tool further comprises a plurality ofposition sensors disposed at close proximity to the rotor to providerotational position signals of the rotor to the control unit. In anembodiment, the controller is configured to control the switchingoperation of the power switch circuit based on the position signals toappropriately energize the stator windings within the correspondingphases.

According to an embodiment, within each phase of the motor, thecontroller is configured to activate a drive signal for a correspondingone of the plurality of power switches within a conduction bandcorresponding to the phase of the motor.

In an embodiment, the controller is configured to set a pulse-widthmodulation (PWM) duty cycle according to a desired speed of the motorand control the drive signal to turn the corresponding one of theplurality of power switches on and off periodically within theconduction band in accordance with the PWM duty cycle to enable variablespeed operation of the motor at constant load.

In an embodiment, the link capacitor has a capacitance value of lessthan or equal to approximately 50 μF.

In an embodiment, the controller is configured to control the switchingoperation of the power switch circuit via one or more drive signals at afixed pulse-width modulation (PWM) duty cycle, the controller settingthe fixed PWM duty cycle to a first value in relation to the firstnominal voltage when powered by the first power supply and to a secondvalue different from the first value and in relation to the secondnominal voltage when powered by the second power supply.

In an embodiment, the controller is configured to control the switchingoperation of the power switch circuit via one or more drive signals at apulse-width modulation (PWM) duty cycle up to a threshold value, thecontroller setting the threshold value to a first value in relation tothe first nominal voltage when powered by the first power supply and toa second value different from the first value and in relation to thesecond nominal voltage when powered by the second power supply.

In an embodiment, the controller is configured to control the switchingoperation of the power switch circuit within a first duty cycle rangewhen coupled to the first power supply, and control the switchingoperation of the power switch circuit within a second duty cycle rangewhen coupled to the second power supply, wherein the second PWM dutycycle range is smaller than the first duty cycle range, in order tooptimize an effective supply of power to the motor when powered by theeither the first or the second power supplies to correspond to theoperating voltage range of the motor.

In an embodiment, the controller is configured to receive a measure ofinstantaneous current on the DC bus line and enforce a current limit oncurrent through the power switch circuit by comparing instantaneouscurrent measures to the current limit and, in response to aninstantaneous current measure exceeding the current limit, turning offthe plurality of power switches for a remainder of a present timeinterval to interrupt current flowing to the electric motor, whereduration of each time interval is fixed as a function of the givenfrequency at which the electric motor is controlled by the controller.

In an embodiment, the controller turns on select power switches at endof the present time interval and thereby resumes current flow to themotor.

In an embodiment, the duration of each time interval is approximatelyten times an inverse of the given frequency at which the motor iscontrolled by the controller. In an embodiment, the duration of eachtime interval is on the order to 100 microseconds.

In an embodiment, duration of the each time interval corresponds to aperiod of pulse-width modulation (PWM) cycle.

In an embodiment, the controller is configured to receive a measure ofcurrent on the DC bus line and enforce a current limit on currentthrough the power switch circuit by setting or adjusting a PWM dutycycle of the one or more drive signals. In an embodiment, the controlleris configured to monitor the current through the DC bus line and adjustthe PWM duty cycle if the current through the DC bus line exceeds thecurrent limit.

In an embodiment, the controller is configured to set the current limitaccording to a voltage rating of one of the first or second powersupplies.

In an embodiment, the controller is configured to set the current limitto a first threshold when the power tool is powered by the first powersupply and to a second threshold when the power tool is powered by thesecond power supply, wherein the second threshold is higher than thefirst threshold, in order to optimize an effective supply of power tothe motor from either the first or the second power supplies tocorrespond to the operating voltage range of the motor.

According to an embodiment, the controller is configured to activate adrive signal within each phase of the motor for a corresponding one ofthe plurality of power switches within a conduction band (CB)corresponding to the phase of the motor. According to an embodiment, theCB is set to approximately 120 degrees.

In an embodiment, the controller is configured to shift the CB by anadvance angle (AA) such that the CB leads ahead of a backelectro-magnetic field (EMF) current of the motor. According to anembodiment, the AA is set to approximately 30 degrees.

In an embodiment, the controller is configured to set at least one ofthe CB or AA according to a voltage rating of one or more of the firstor the second power supplies.

In an embodiment, the controller is configured to set the CB to a firstCB value when the power tool is powered by the first power supply and toa second CB value greater than the first CB value when the power tool ispowered by the second power supply. In an embodiment, the second CBvalue is determined so as to boost or reduce an effective supply ofpower to the motor when powered by either the first or the second powersupplies to correspond to the operating voltage range of the motor. Inan embodiment, first CB value is approximately 120 degrees and thesecond CB value is greater than approximately 130 degrees.

In an embodiment, the controller is configured to the AA to a first AAvalue when the power tool is powered by the first power supply to asecond AA value greater than the first AA value when the power tool ispowered by the second power supply. In an embodiment, the second AAvalue is determined so as to boost or reduce an effective supply ofpower to the motor when powered by either the first or the second powersupplies to correspond to the operating voltage range of the motor. Inan embodiment, first AA value is approximately 30 degrees and the secondAA value is greater than approximately 35 degrees.

In an embodiment, the controller is configure to set the CB and AA intandem according to the voltage rating of the first or the second powersupplies.

In an embodiment, the controller is configured to set at least one ofthe CB or AA to a base value corresponding to a maximum speed of themotor at approximately no load, and gradually increase the at least oneof CB or AA from the base value to a threshold value in relation to anincrease in torque to yield a substantially linear speed-torque curve.In an embodiment, the controller is configured to maintain substantiallyconstant speed on the speed-torque curve. In an embodiment, the basevalue and the threshold value corresponds to a low torque range withinwhich the speed-torque curve is substantially linear. In an embodiment,the controller is configured to maintain the at least one of CB or AA atthe torque greater than the low torque range.

In another aspect, a battery pack is convertible back and forth betweena low rated voltage/high capacity configuration and a medium ratedvoltage/low capacity configuration.

In another aspect, a power tool system includes a battery pack that isconvertible back and forth between a low rated voltage/high capacityconfiguration and a medium rated voltage/low capacity configuration anda power tool that couples with the battery pack, converts the batterypack from the low rated voltage/high capacity configuration to themedium rated voltage/low capacity configuration and operates with thebattery pack in its medium rated voltage/low capacity configuration.

In another aspect, a power tool system includes a battery pack that isconvertible back and forth between a low rated voltage/high capacityconfiguration and a medium rated voltage/low capacity configuration, afirst power tool that couples with the battery pack, converts thebattery pack from the low rated voltage/high capacity configuration tothe medium rated voltage/low capacity configuration and operates withthe battery pack its medium rated voltage/low capacity configuration anda second power tool that couples with the battery pack and operates withthe battery pack in its low rated voltage/high capacity configuration.

In another aspect, a power tool system includes a first battery packthat is convertible back and forth between a low rated voltage/highcapacity configuration and a medium rated voltage/low capacityconfiguration, a second battery pack that is always in a low ratedvoltage/high capacity configuration and a power tool that couples withthe first battery pack and operates with the first battery pack in itslow rated voltage/high capacity configuration and couples with thesecond battery pack and operates with the second battery pack in its lowrated voltage/high capacity configuration.

In another aspect, a power tool system includes a first battery packthat is convertible back and forth between a low rated voltage/highcapacity configuration and a medium rated voltage/low capacityconfiguration, a second battery pack that is always in a low ratedvoltage/high capacity configuration, a first power tool power tool thatcouples with the first battery pack and operates with the first batterypack in its low rated voltage/high capacity configuration and coupleswith the second battery pack and operates with the second battery packin its low rated voltage/high capacity configuration and a second powertool that couples with the first battery pack but not the second batterypack and operates with the first battery pack in its high ratedvoltage/low capacity configuration.

In another aspect, a power tool system includes a battery pack that isconvertible back and forth between a low rated voltage/high capacityconfiguration and a medium rated voltage/low capacity configuration, afirst, medium rated voltage power tool that couples with the batterypack, converts the battery pack from the low rated voltage/high capacityconfiguration to the medium rated voltage/low capacity configuration andoperates with the battery pack in its medium rated voltage/low capacityconfiguration and a second, high rated voltage power tool that coupleswith a plurality of the battery packs, converts each battery pack fromthe low rated voltage/high capacity configuration to the medium ratedvoltage/low capacity configuration and operates with the battery packsin their medium rated voltage/low capacity configuration.

In another aspect, a power tool system includes a battery pack that isconvertible back and forth between a low rated voltage/high capacityconfiguration and a medium rated voltage/low capacity configuration, ahigh rated voltage power tool that couples with a plurality of thebattery packs, converts each battery pack from the low ratedvoltage/high capacity configuration to the medium rated voltage/lowcapacity configuration and/or couples with a high rated voltagealternating current power supply and operates at a high rated voltagewith either the battery packs in their medium rated voltage/low capacityconfiguration and/or the high rated voltage alternating current powersupply.

In another aspect, a first battery pack is convertible back and forthbetween a low rated voltage/high capacity configuration and a mediumrated voltage/low capacity configuration a second battery pack that isalways in a low rated voltage/high capacity configuration and a batterypack charger is electrically and mechanically connectable to the firstbattery pack and the second battery pack is able to charger both thefirst battery pack and the second battery pack.

In another aspect, a battery pack includes a housing and a batteryresiding in the housing. The battery may include a plurality ofrechargeable cells and a switching network coupled to the plurality ofrechargeable cells. The switching network may have a first configurationand a second configuration. The switching network may be switchable fromthe first configuration to the second configuration and from the secondconfiguration to the first configuration. The plurality of rechargeablecells may be in a first configuration when the switching network is inthe first configuration and a second configuration when the switchingnetwork is in the second configuration. The second configuration isdifferent than the first configuration.

The switching network of the battery pack of this embodiment may have athird configuration wherein the plurality of rechargeable cells is in athird configuration when the switching network is in the thirdconfiguration. The switching network of the battery pack of thisembodiment may be switched between the first configuration and thesecond configurations by an external input to the battery pack. Thefirst configuration of the rechargeable cells of the battery pack ofthis embodiment may be a relatively low voltage and high capacityconfiguration and the second configuration of the rechargeable cells ofthe battery pack may be a relatively high voltage and low capacityconfiguration. The battery pack of this embodiment may include cellconfigurations in which the first configuration provides a first ratedpack voltage and the second configuration provides a second rated packvoltage, wherein the first rated pack voltage is different than thesecond rated pack voltage. The third configuration of the battery packof this embodiment may be an open circuit configuration.

The rechargeable cells of the battery pack of the first configurationmay enter the third configuration upon converting between the first andsecond configurations. The battery pack of this embodiment may comprisea terminal block coupled to the plurality of rechargeable cells and theswitching network, wherein the terminal block receives a switchingelement to switch the switching network from the first configuration tothe second configuration.

In another aspect, a battery pack comprises a housing and a batteryresiding in the housing. The battery may include a set P of Orechargeable cells Q where O is a number ≥2. The set P of rechargeablecells Q may include N subsets R of cells Q where N is a number ≥2. Eachsubset R of cells Q may include M cells Q, where M is a number ≥1, whereM×N=O. The battery may include a switching network coupled to therechargeable cells, wherein the switching network may have a firstconfiguration and a second configuration and may be switchable from thefirst configuration to the second configuration and from the secondconfiguration to the first configuration. All of the subsets R ofrechargeable cells Q may be connected in parallel when the switchingnetwork is in the first configuration and disconnected when theswitching network is in the second configuration. A first power terminalmay be coupled to a positive terminal of cell Q1 and a second powerterminal may be coupled to a negative terminal of QO wherein the firstand second power terminals provide power out from the battery pack. Anegative conversion terminal may be coupled to a negative terminal ofeach subset R1 through RN-1 and a positive conversion terminal may becoupled to a positive terminal of each subset R2 through RN. Thenegative conversion terminal and the positive conversion terminal of thebattery pack of this embodiment are accessible from outside the batteryhousing.

In another aspect, a battery pack comprises a housing and a batteryresiding in the housing. The battery of this embodiment may include abattery residing in the housing. The battery of this embodiment mayinclude a set P of O rechargeable cells Q, where O is a number ≥2. Theset P of rechargeable cells Q may include N subsets R of cells Q, whereN is a number ≥2. Each subset R of cells Q may include M cells Q where Mis a number ≥1, where M×N=O. The battery pack of this embodiment mayinclude a switching network coupled to the rechargeable cells. Theswitching network may have a first configuration and a secondconfiguration and may be switchable from the first configuration to thesecond configuration and from the second configuration to the firstconfiguration. All of the subsets R of rechargeable cells Q may beconnected in parallel when the switching network is in the firstconfiguration and disconnected when the switching network is in thesecond configuration. The battery pack may include a first powerterminal coupled to a positive terminal of Q1 and a second powerterminal coupled to a negative terminal of QO wherein the first andsecond power terminals provide power out from the battery pack. Thebattery pack may include a negative conversion terminal coupled to anegative terminal of each subset of cells and a positive conversionterminal coupled to a positive terminal of each subset of cells.

In another aspect, a power tool comprises: a first power supply from anAC input having a rated AC voltage; a second power supply from aplurality of rechargeable battery cells having the rated DC voltage; amotor coupleable to the first power supply and the second power supply;and a control circuit configured to operate the motor with substantiallythe same output power when operating on the first power supply and thesecond power supply. The rated DC voltage of the power tool of thisembodiment may be approximately equal to the rated AC voltage. The motorof the power tool of this embodiment is a brushed motor. The controlcircuit of the power tool of this embodiment may operate the brushedmotor at a constant no load speed regardless of whether the motor isoperating on the first power supply or the second power supply. Thecontrol circuit of the power tool of this embodiment may operate thebrushed motor at a variable no load speed based upon a user input. Thecontrol circuit of the power tool of this embodiment may include anIGBT/MOSFET circuit configured to operate the motor at a variable noload speed using either the first power supply or the second powersupply. The motor of the power tool of this embodiment may be abrushless motor. The control circuit of the power tool of thisembodiment may comprise a small capacitor and a cycle by cycle currentlimiter. The rated DC voltage of the power tool of this embodiment maybe less than the rated AC voltage. The control circuit of the power toolof this embodiment may comprise a small capacitor and a cycle by cyclecurrent limiter. The control circuit power tool of this embodiment maycomprise at least one of advance angle and conduction band controls. Thecontrol circuit of the power tool of this embodiment may detect whetherthe first power supply and the second power supply are activated. Thecontrol circuit of the power tool of this embodiment may select thefirst power supply whenever it is active. The control circuit of thepower tool of this embodiment may switch to the second power supply inthe event that the first power supply becomes inactive. The controlcircuit of the power tool of this embodiment may include a boost modewhereby the control circuit operates the power supply at a higher outputpower using both the first power supply and the second power supplysimultaneously. The power supply of the power tool of this embodimentmay be provided by a cordset. The first power supply and the secondpower supply of the power tool of this embodiment may provide power tothe motor simultaneously and may provide substantially more power thaneither the first or the second power supplies could provideindividually.

In another aspect, a power tool comprises an input for receiving powerfrom an AC power supply; an input for receiving power from arechargeable DC power supply; a charger for charging the rechargeable DCpower supply with the AC power supply; and a motor configured to bepowered by at least one of the AC power supply and the rechargeable DCpower supply. The AC power supply of the power tool of this embodimentmay be a mains line. The rechargeable DC power supply of the power toolof this embodiment may be a removable battery pack.

In another aspect, a power tool comprises a power tool comprising aninput for receiving AC power from an AC power source, the AC powersource having a rated AC voltage, the AC power source external to thepower tool; an input for receiving DC power from a DC power source, theDC power source having a rated DC voltage, the DC power source being aplurality of rechargeable battery cells, the rated DC voltageapproximately equal to the rated AC voltage; and a motor configured tobe powered by at least one of the AC power source and the DC powersource. The AC power source of the power tool of this embodiment may bea mains line. The rechargeable DC power supply of the power tool of thisembodiment may be a battery pack. The AC power supply and the DC powersupply of the power tool of this embodiment may have a rated voltage of120 volts.

In another aspect, a power tool comprises a motor; a first power supplyfrom an AC input line; a second power supply from a rechargeablebattery, the second power supply providing power approximatelyequivalent to the power of the first power supply. The first powersupply and the second power supply of the power tool of this embodimentmay provide power to the motor simultaneously. The first power supplyand the second power supply of the power tool of this embodiment mayprovide power to the motor alternatively.

In another aspect, a power tool comprises a motor; a first power supplyfrom an AC input line; a second power supply from a rechargeablebattery, the second power supply providing power approximatelyequivalent to the power of the first power supply. The first powersupply and the second power supply of the power tool of this embodimentmay provide power to the motor simultaneously. The first power supplyand the second power supply of the power tool of this embodiment mayprovide power to the motor alternatively.

In another aspect, a battery pack may include: a housing; a plurality ofcells; and a converter element, the converter element moveable between afirst position wherein the plurality of cells are configured to providea first rated voltage and a second position wherein the plurality ofcells are configured to provide a second rated voltage different thanthe first rated voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a power tool system.

FIG. 1B is a schematic diagram of one particular implementation of apower tool system.

FIGS. 2A-2C are exemplary simplified circuit diagrams of battery cellconfigurations of a battery.

FIG. 3A is a schematic diagram of a set of low rated voltage DC powertool(s), a set of DC battery pack power supply(ies), and a set ofbattery pack charger(s) of the power tool system of FIG. 1A.

FIG. 3B is a schematic diagram of a set of medium rated voltage DC powertool(s), a set of DC battery pack power supply(ies), and a set ofbattery pack charger(s) of the power tool system of FIG. 1A.

FIG. 3C is a schematic diagram of a set of high rated voltage DC powertool(s), a set of DC battery pack power supply(ies), and a set ofbattery pack charger(s) of the power tool system of FIG. 1A.

FIG. 4 is a schematic diagram of a set of high rated voltage AC/DC powertool(s), a set of DC battery pack power supply(ies), a set of AC powersupply(ies), and a set of battery pack charger(s) of the power toolsystem of FIG. 1A.

FIGS. 5A-5B are schematic diagrams of classifications of AC/DC powertools of the power tool system of FIG. 1A.

FIG. 6A depicts an exemplary system block diagram of a constant-speedAC/DC power tool with a universal motor, according to an embodiment.

FIG. 6B depicts an exemplary system block diagram of the constant-speedAC/DC power tool of FIG. 6A additionally provided with an exemplarypower supply switching unit, according to an embodiment.

FIG. 6C depicts an exemplary system block diagram of the constant-speedAC/DC power tool of FIG. 6A additionally provided with an alternativeexemplary power supply switching unit, according to an embodiment.

FIG. 6D depicts an exemplary system block diagram of the constant-speedAC/DC power tool of FIG. 6A additionally provided with yet anotherexemplary power supply switching unit, according to an embodiment.

FIG. 6E depicts an exemplary system block diagram of a constant-speedAC/DC power tool with a universal motor where power supplied from an ACpower supply has a nominal voltage significantly different from nominalvoltage provided from a DC power supply, according to an embodiment.

FIG. 7A depicts an exemplary system block diagram of a variable-speedAC/DC power tool with a universal motor, according to an embodiment.

FIG. 7B depicts an exemplary system block diagram of the constant-speedAC/DC power tool of FIG. 7A additionally provided with a power supplyswitching unit, according to an embodiment.

FIGS. 7C-7E depict exemplary circuit diagrams of various embodiments ofa DC switch circuit.

FIG. 7F depicts an exemplary system block diagram of a variable-speedAC/DC power tool with a universal motor having an integrated AC/DC powerswitching circuit, according to an alternative embodiment.

FIGS. 7G and 7H depict exemplary circuit diagrams of various embodimentsof the integrated AC/DC power switching circuit.

FIG. 8A depicts an exemplary system block diagram of a constant-speedAC/DC power tool with a brushed direct-current (DC) motor, according toan embodiment.

FIG. 8B depicts an exemplary system block diagram of the constant-speedAC/DC power tool of FIG. 8A additionally provided with an exemplarypower supply switching unit, according to an embodiment.

FIG. 8C depicts an exemplary system block diagram of a constant-speedAC/DC power tool with a brushed DC motor where power supplied from an ACpower supply has a nominal voltage significantly different from nominalvoltage provided from a DC power supply, according to an embodiment.

FIG. 8D depicts another exemplary system block diagram of aconstant-speed AC/DC power tool with a brushed DC motor where powersupplied from an AC power supply has a nominal voltage significantlydifferent from nominal voltage provided from a DC power supply,according to an alternative embodiment.

FIG. 9A depicts an exemplary system block diagram of a variable-speedAC/DC power tool with a brushed DC motor, according to an embodiment.

FIG. 9B depicts an exemplary system block diagram of the constant-speedAC/DC power tool of FIG. 9A additionally provided with a power supplyswitching unit, according to an embodiment.

FIG. 10A depicts an exemplary system block diagram of an AC/DC powertool with a three-phase brushless DC motor having a power supplyswitching unit and a motor control circuit, according to an embodiment.

FIG. 10B depicts an exemplary system block diagram of the AC/DC powertool of FIG. 10A having an alternative power supply switching unit,according to an embodiment.

FIG. 10C depicts an exemplary power switch circuit having a three-phaseinverter bridge, according to an embodiment.

FIG. 11A depicts an exemplary waveform diagram of a drive signal for thepower switch circuit within a single conduction band of a phase of themotor at various pulse-width modulation (PWM) duty cycle levels forvariable-speed operation of the brushless motor, according to anembodiment.

FIG. 11B depicts an exemplary current-time waveform implementing anexemplary 20 amp cycle-by-cycle current limit, according to anembodiment.

FIG. 11C depicts an exemplary flowchart for implementing cycle-by-cyclecurrent limits.

FIG. 12A depicts an exemplary waveform diagram of a pulse-widthmodulation (PWM) drive sequence of the three-phase inventor bridgecircuit FIG. 10C within a full 360 degree conduction cycle, where eachphase is being driven at a 120 degree conduction band (CB), according toan embodiment.

FIG. 12B depicts an exemplary waveform diagram of the drive sequence ofFIG. 12A operating at full-speed, according to an embodiment.

FIG. 12C depicts an exemplary waveform diagram corresponding to thedrive sequence of FIG. 12B with an advance angle (AA) of Y=30°,according to an embodiment.

FIG. 12D depicts an exemplary speed-torque waveform diagram of anexemplary high powered tool showing the effect of increasing AA at afixed CB of 120° on the speed/torque profile, according to anembodiment.

FIG. 12E depicts an exemplary power-torque waveform diagram of the samehigh powered tool showing the effect of increasing AA at a fixed CB of120° on the power/torque profile, according to an embodiment.

FIG. 12F depicts an exemplary efficiency-torque waveform diagram of thesame high powered tool showing the effect of increasing AA at a fixed CBof 120° on the efficiency/torque profile, according to an embodiment.

FIG. 13A depicts an exemplary waveform diagram of the drive sequence ofthe three-phase inventor bridge circuit, where each phase is beingdriven at CB of 150°, according to an embodiment.

FIG. 13B depicts an exemplary waveform diagram of the drive sequence ofthe three-phase inventor bridge circuit, where each phase is beingdriven at CB of 150° with an AA of Y=30°, according to an embodiment.

FIG. 13C depicts an exemplary speed-torque waveform diagram of anexemplary high powered tool showing the effect of increasing CB and AAin tandem on the speed/torque profile, according to an embodiment.

FIG. 13D depicts an exemplary power-torque waveform diagram of the samehigh powered tool showing the effect of increasing CB and AA in tandemon the power/torque profile, according to an embodiment.

FIG. 13E depicts an exemplary efficiency-torque waveform diagram of thesame high powered tool showing the effect of increasing CB and AA intandem on the efficiency/torque profile, according to an embodiment.

FIG. 13F depicts an exemplary improved speed-torque waveform diagram ofan exemplary high powered tool using variable CB/AA, according to anembodiment.

FIG. 13G depicts another improved speed-torque waveform diagram of thesame high powered tool using variable CB/AA, according to an alternativeembodiment.

FIG. 14A depicts an exemplary maximum power output contour map for anexemplary power tool based on various CB and AA values, according to analternative embodiment.

FIG. 14B depicts an exemplary efficiency contour map for the same powertool based on various CB and AA values, according to an alternativeembodiment.

FIG. 14C depicts an exemplary combined efficiency and maximum poweroutput contour map for the same power tool based on various CB and AAvalues, according to an alternative embodiment.

FIG. 14D depicts an exemplary contour map showing optimal combinedefficiency and maximum power output contours at various input voltagelevels, according to an alternative embodiment.

FIG. 15A depicts an exemplary waveform diagram of the rectified ACwaveform supplied to the motor control circuit under a loaded condition,according to an embodiment.

FIG. 15B depicts an exemplary rectified voltage waveform diagram and acorresponding current waveform diagram using a relatively largecapacitor on a rectified AC power line (herein referred to as DC busline), according to an embodiment.

FIG. 15C depicts an exemplary rectified voltage waveform diagram and acorresponding current waveform diagram using a relatively medium-sizedcapacitor on the DC bus line, according to an embodiment.

FIG. 15D depicts an exemplary rectified voltage waveform diagram and acorresponding current waveform diagram using a relatively smallcapacitor on the DC bus line, according to an embodiment.

FIG. 15E depicts an exemplary combined diagram showing poweroutput/capacitance, and average DC bus voltage/capacitance waveforms atvarious RMS current ratings, according to an embodiment.

DETAILED DESCRIPTION

I. Power Tool System

Referring to FIG. 1A, in one embodiment, a power tool system 1 includesa set of power tools 10 (which include DC power tools 10A and AC/DCpower tools 10B), a set of power supplies 20 (which include DC batterypack power supplies 20A and AC power supplies 20B), and a set of batterypack chargers 30. Each of the power tools, power supplies, and batterypack chargers may be said to have a rated voltage. As used in thisapplication, rated voltage may refer to one or more of the advertisedvoltage, the operating voltage, the nominal voltage, or the maximumvoltage, depending on the context. The rated voltage may also encompassa single voltage, several discrete voltages, or one or more ranges ofvoltages. As used in the application, rated voltage may refer to any ofthese types of voltages or a range of any of these types of voltages.

Advertised Voltage.

With respect to power tools, battery packs, and chargers, the advertisedvoltage generally refers to a voltage that is designated on labels,packaging, user manuals, instructions, advertising, marketing, or othersupporting documents for these products by a manufacturer or seller sothat a user is informed which power tools, battery packs, and chargerswill operate with one another. The advertised voltage may include anumeric voltage value, or another word, phrase, alphanumeric charactercombination, icon, or logo that indicates to the user which power tools,battery packs, and chargers will work with one another. In someembodiments, as discussed below, a power tool, battery pack, or chargermay have a single advertised voltage (e.g., 20V), a range of advertisedvoltages (e.g., 20V-60V), or a plurality of discrete advertised voltages(e.g., 20V/60V). As discussed further below, a power tool may also beadvertised or labeled with a designation that indicates that it willoperate with both a DC power supply and an AC power supply (e.g., AC/DCor AC/60V). An AC power supply may also be said to have an advertisedvoltage, which is the voltage that is generally known in common parlanceto be the AC mains voltage in a given country (e.g., 120 VAC in theUnited States and 220 VAC-240 VAC in Europe).

Operating Voltage.

For a power tool, the operating voltage generally refers to a voltage ora range of voltages of AC and/or DC power supply(ies) with which thepower tool, its motor, and its electronic components are designed tooperate. For example, a power tool advertised as a 120V AC/DC tool mayhave an operating voltage range of 92V-132V. The power tool operatingvoltage may also refer to the aggregate of the operating voltages of aplurality of power supplies that are coupled to the power tool (e.g., a120V power tool may be operable using two 60V battery packs connected inseries). For a battery pack and a charger, the operating voltage refersto the DC voltage or range of DC voltages at which the battery pack orcharger is designed to operate. For example, a battery pack or chargeradvertised as a 20V battery pack or charger may have an operatingvoltage range of 17V-19V. For an AC power supply, the operating voltagemay refer either to the root-mean-square (RMS) of the voltage value ofthe AC waveform and/or to the average voltage within each positivehalf-cycle of the AC waveform. For example, a 120 VAC mains power supplymay be said to have an RMS operating voltage of 120V and an averagepositive operating voltage of 108V.

Nominal Voltage.

For a battery pack, the nominal voltage generally refers to the averageDC voltage output from the battery pack. For example, a battery packadvertised as a 20V battery pack, with an operating voltage of 17V-19V,may have a nominal voltage of 18V. For an AC power supply, the operatingvoltage may refer either to the root-mean-square (RMS) of the voltagevalue of the AC waveform and/or to the average voltage within eachpositive half-cycle of the AC waveform. For example, a 120 VAC mainspower supply may be said to have an RMS nominal voltage of 120V and anaverage positive nominal voltage of 108V.

Maximum Voltage.

For a battery pack, the maximum voltage may refer to the fully chargedvoltage of the battery pack. For example, a battery pack advertised as a20V battery pack may have a maximum fully charged voltage of 20V. For acharger, the maximum voltage may refer to the maximum voltage to which abattery pack can be recharged by the charger. For example, a 20V chargermay have a maximum charging voltage of 20V.

It should also be noted that certain components of the power tools,battery packs, and chargers may themselves be said to have a voltagerating, each of which may refer to one or more of the advertisedvoltage, the operating voltage, the nominal or voltage, or the maximumvoltage. The rated voltages for each of these components may encompass asingle voltage, several discrete voltages, or one or more ranges ofvoltages. These voltage ratings may be the same as or different from therated voltage of power tools, battery packs and chargers. For example, apower tool motor may be said to have its own an operating voltage orrange of voltages at which the motor is designed to operate. The motorrated voltage may be the same as or different from the operating voltageor voltage range of the power tool. For example, a power tool having avoltage rating of 60V-120V may have a motor that has an operatingvoltage of 60V-120V or a motor that has an operating voltage of90V-100V.

The power tools, power supplies, and chargers also may have ratings forfeatures other than voltage. For example, the power tools may haveratings for motor performance, such as an output power (e.g., maximumwatts out (MWO) as described in U.S. Pat. No. 7,497,275, which isincorporated by reference) or motor speed under a given load condition.In another example, the battery packs may have a rated capacity, whichrefers to the total energy stored in a battery pack. The battery packrated capacity may depend on the rated capacity of the individual cellsand the manner in which the cells are electrically connected.

This application also refers to the ratings for voltage (and otherfeatures) using relative terms such as low, medium, high, and very high.The terms low rated, medium rated, high rated, and very high rated arerelative terms used to indicate relative relationships between thevarious ratings of the power tools, battery packs, AC power supplies,chargers, and components thereof, and are not intended to be limited toany particular numerical values or ranges. For example, it should beunderstood that a low rated voltage is generally lower than a mediumrated voltage, which is generally lower than a high rated voltage, whichis generally lower than a very high rated voltage. In one particularimplementation, the different rated voltages may be whole numbermultiples or factors of each other. For example, the medium ratedvoltage may be a whole number multiple of the low rated voltage, and thehigh rated voltage may be a whole number multiple of the medium ratedvoltage. For example, the low rated voltage may be 20V, the medium ratedvoltage may be 60V (3×20V), and the high rated voltage may be 120V(2×60V and 6×20V). In this application, the designation “XY” maysometimes be used as a generic designation for the terms low, medium,high, and very high.

In some instances, a power tool, power supply, or charger may be said tohave multiple rated voltages. For example, a power tool or a batterypack may have a low/medium rated voltage or a medium/high rated voltage.As discussed in more detail below, this multiple rating refers to thepower tool, power supply, or charger having more than one maximum,nominal or actual voltage, more than one advertised voltage, or beingconfigured to operate with two or more power tools, battery packs, ACpower supplies, or chargers, having different rated voltages from eachother. For example, a medium/high rated voltage power tool may labeledwith a medium and a high voltage, and may be configured to operate witha medium rated voltage battery pack or a high rated voltage AC powersupply. It should be understood that a multiply rated voltage may meanthat the rated voltage comprises a range that spans two different ratedvoltages or that the rated voltage has two discrete different ratedvalues.

This application also sometimes refers to a first one of a power tool,power supply, charger, or components thereof as having a first ratedvoltage that corresponds to, matches, or is equivalent to a second ratedvoltage of a second one of a power tool, power supply, charger, orcomponents thereof. This comparison generally refers to the first ratedvoltage having one or more value(s) or range(s) of values that aresubstantially equal to, overlap with, or fall within one or morevalue(s) or range(s) of values of the second rated voltage, or that thefirst one of the power tool, power supply, charger, or components, isconfigured to operate with the second one of the power tool, powersupply, charger, or components thereof. For example, an AC/DC power toolhaving a rated voltage of 120V (advertised) or 90V-132V (operating) maycorrespond to a pair of battery packs having a total rated voltage of120V (advertised and maximum), 108V (nominal) or 102V-120V (operating),and to several AC power supplies having a rated voltages ranging from of100 VAC-120 VAC.

Conversely, this application sometimes refers to a first one of a powertool, power supply, charger, or components thereof as having a firstrated voltage that does not correspond to, that is different from, orthat is not equivalent to a second rated voltage of a second one of apower tool, power supply, charger, or components thereof. Thesecomparisons generally refer to the first rated voltage having one ormore value(s) or range(s) of values that are not equal to, do notoverlap with, or fall outside one or more value(s) or range(s) of valuesof the second rated voltage, or that the first one of the power tool,power supply, charger, or components thereof are not configured tooperate with the second one of the power tool, power supply, chargers,or components thereof. For example, an AC/DC power tool having the ratedvoltage of 120V (advertised) or 90V-132V (operating) may not correspondto a battery packs having a total rated voltage of 60V (advertised andmaximum), 54V (nominal) or 51V-60V (operating), or to AC power supplieshaving a rated voltages ranging from of 220 VAC-240 VAC.

Referring again to FIG. 1A, the power tools 10 include a set ofcordless-only or DC power tools 10A and a set of corded/cordless orAC/DC power tools 10B. The set of DC power tools 10A may include a setof low rated voltage DC power tools 10A1 (e.g., under 40V, such as 4V,8V, 12V, 18V, 20V, 24V and/or 36V), a set of medium rated voltage DCpower tools 10A2 (e.g., 40V to 80V, such as 40V, 54V, 60V, 72V, and/or80V), and a set of high rated voltage DC power tools 10A3 (e.g., 100V to240V, such as 100V, 110V, 120V, 220V, 230V and/or 240V). It may also besaid that the high rated voltage DC power tools include a subset of highrated voltage DC power tools (e.g., 100V to 120V, such as 100V, 110V, or120V for, e.g., the United States, Canada, Mexico, and Japan) and asubset of very high rated voltage DC power tools (e.g., 220V to 240V,such as 220V, 230V, or 240V for, e.g., most countries in Europe, SouthAmerica, Africa, and Asia). For convenience, the high rated and veryhigh rated voltage DC power tools are referred to collectively as a setof high rated voltage DC power tools 10A3.

The AC/DC power tools 10B generally have a rated voltage thatcorresponds to the rated voltage for an AC mains supply in the countriesin which the tool will operate or is sold (e.g., 100V to 120V, such as100V, 110V, or 120V in countries such as the United States, Canada,Mexico, and Japan, and 220V to 240V, such as 220V, 230V and/or 240V inmost countries in Europe, South America, Asia and Africa). In someinstances, these high rated voltage AC/DC power tools 10B arealternatively referred to as AC-rated AC/DC power tools, where AC ratedrefers to the fact that the high voltage rating of the AC/DC power toolscorrespond to the voltage rating of the AC mains power supply in acountry where the power tool is operable and/or sold. For convenience,the high rated and very high rated voltage AC/DC power tools arereferred to collectively as a set of high rated voltage AC/DC powertools 10B.

A. Power Supplies

The set of power supplies 20 may include a set of DC battery pack powersupplies 20A and a set of AC power supplies 20B. The set of DC batterypack power supplies 20A may include one or more of the following: a setof low rated voltage battery packs 20A1 (e.g., under 40V, such as 4V,8V, 12V, 18V, 20V, 24V and/or 36V), a set of medium rated voltagebattery packs 20A2 (e.g., 40V to 80V, such as 40V, 54V, 60V, 72V and/or80V), a set of high rated voltage battery packs 20A3 (e.g., 100V to 120Vand 220V to 240V, such as 100V, 110V, 120V, 220V, 230V and/or 240V), anda set of convertible voltage range battery packs 20A4 (discussed ingreater detail below). The AC power supplies 20B may include powersupplies that have a high voltage rating that correspond to the voltagerating of an AC power supply in the countries in which the tool isoperable and/or sold (e.g., 100V to 120V, such as 100V, 110V, or 120V,in countries such as the United States, Canada, Mexico, and Japan, and220V to 240V, such as 220V, 230V and/or 240V in most countries inEurope, South America, Asia and Africa). The AC power supplies maycomprise an AC mains power supply or an alternative power supply with asimilar rated voltage, such as an AC generator or another portable ACpower supply.

One or more of the DC battery pack power supplies 20A are configured topower one or more of the set of low rated voltage DC power tools 10A1,the set of medium rated voltage DC power tools 10A2, and the set of highrated voltage DC power tools 10A3, as described further below. The AC/DCpower tools 10B may be powered by one or more of the DC battery packpower supplies 20A or by one or more of the AC power supplies 20B. FIGS.111-114 of U.S. Pat. No. 9,406,915, which is incorporated herein byreference, illustrate an exemplary embodiment of an AC/DC power toolinterface 22B for providing AC power from the AC power supply 20B to theAC/DC power tool 10B. The AC/DC power tool interface 22B includes ahousing 23 and a cord 25 including a two or three pronged plug (notshown) at a first end and a coupled to the housing 23 at a second end.The housing 23 includes a pair of DC power tool interfaces 27 that aresubstantially equivalent in shape and size as the DC power toolinterface 22A of the DC battery pack power supply 20A. The housing 23also includes a three pronged receptacle 29 (or alternatively a twopronged receptacle) positioned between the pair of DC power toolinterfaces 27. The illustrated AC/DC power tool interface 22B of the ACpower supply 20B is received in an exemplary power supply interface 16of an AC/DC power tool illustrated and described below in FIGS. 114 and115. As illustrated in FIG. 113 of U.S. Pat. No. 9,406,915, the AC/DCpower tool interface 22B may include a circuit 31 for receiving “dirty”AC signals from certain AC power supplies, for example, gas poweredgenerators. The set of battery pack chargers 30 includes one or morebattery pack chargers 30 configured to charge one or more of the DCbattery pack power supplies 20A. Below is a more detailed description ofthe power supplies 20, the battery pack chargers 30, and the power tools10.

1. DC Battery Pack Power Supplies

Referring to FIG. 1, as noted above, the DC battery pack power supplies20A include a set of low rated voltage battery packs 20A1, a set ofmedium rated voltage battery packs 20A2, a set of high rated voltagebattery packs 20A3, and a set of convertible battery packs 20A4. Eachbattery pack may include a housing, a plurality of cells, and a powertool interface that is configured to couple the battery pack to a powertool or to a charger. Each cell has a rated voltage, usually expressedin volts (V), and a rated capacity (referring to the energy stored in acell), usually expressed in amp-hours (Ah). As is well known by those ofordinary skill in the art, when cells in a battery pack are connected toeach other in series the voltage of the cells is additive. When thecells are connected to each other in parallel the capacity of the cellsis additive. The battery pack may include several strings of cells.Within each string, the cells may be connected to each other in series,and each string may be connected to the other cells in parallel. Thearrangement, voltage and capacity of the cells and the cell stringsdetermine the overall rated voltage and rated capacity of the batterypack. Within each set of DC battery pack power supplies 20A, there maybe battery packs having the same voltage but multiple different ratedcapacities, for example, 1.5 Amp-Hours (Ah), 2 Ah, 3 Ah, or 4 Ah.

FIGS. 2A-2C illustrate exemplary battery cell configurations for abattery 24 that is part of the set of DC battery pack power supplies20A. These examples are not intended to limit the possible cellconfigurations of the batteries 24 in each set of DC battery pack powersupplies 20A. FIG. 2A illustrates a battery 24 having five battery cells26 connected in series. In this example, if each of the cells 26 has arated voltage of 4V and a rated capacity of 1.5 Ah this battery 24 wouldhave a rated voltage of 20V and a rated capacity of 1.5 Ah. FIG. 2Billustrates a battery 24 having ten cells. The battery 24 includes fivesubsets 28 of cells 26 with each subset 28 including two cells 26. Thecells 26 of each subset 28 are connected in parallel and the subsets 28are connected in series. In this example, if each of the cells 26 has arated voltage of 4V and a rated capacity of 1.5 Ah this battery 24 wouldhave a rated voltage of 20V and a rated capacity of 3 Ah. FIG. 2Cillustrates a battery 24 having fifteen cells 120. The battery 24includes five subsets 28 of cells 26 with each subset 28 including threecells 26. The cells 26 of each subset 28 are connected in parallel andthe subsets 28 are connected in series. In this example, if each of thecells 26 has a rated voltage of 4V and a rated capacity of 1.5 Ah thisbattery 24 would have a rated voltage of 20V and a rated capacity of 4.5Ah.

a. Low Rated Voltage Battery Packs

Referring to FIGS. 1A and 3A, each of the low rated voltage batterypacks 20A1 includes a DC power tool interface 22A configured to becoupled to a battery pack interface 16A on a corresponding low ratedvoltage power tool 10A1 and to a battery pack interface 16A on acorresponding low rated voltage battery pack charger 30. The DC powertool interface 22A may include a DC power in/out+ terminal, a DC powerin/out− terminal, and a communications (COMM) terminal. The set of lowrated voltage battery packs 20A1 may include one or more battery packshaving a first rated voltage and a first rated capacity. The first ratedvoltage is, relatively speaking, a low rated voltage, as compared to theother battery packs in the DC battery pack power supplies 20A. Forexample, the low rated voltage battery packs 20A1 may include batterypacks having a rated voltage of 17V-20V (which may encompass anadvertised voltage of 20V, an operating voltage of 17V-19V, a nominalvoltage of 18V, and a maximum voltage of 20V). However, the set of lowrated voltage battery packs 20A1 is not limited to a rated voltage of20V. The set of low rated voltage battery packs 20A1 may have otherrelatively low rated voltages such as 4V, 8V, 12V, 18V, 24V, or 36V.Within the set of low rated voltage battery packs 20A1 there may bebattery packs having the same rated voltage but with different ratedcapacities. For example, the set of low rated voltage battery packs 20A1may include a 20V/1.5 Ah battery pack, a 20V/2 Ah battery pack, a 20V/3Ah battery pack and/or a 20V/4 Ah battery pack. When referring to thelow rated voltage of the set of low rated voltage battery packs 20A1, itis meant that the rated voltage of the set of low rated voltage batterypacks 20A1 is lower than the rated voltage of the set of medium ratedvoltage battery packs 20A2 and the set of high rated voltage batterypacks 20A3.

Examples of battery packs in the set of low rated voltage battery packs120A may include the DEWALT 20V MAX set of battery packs, sold by DEWALTIndustrial Tool Co. of Towson, Md. Other examples of battery packs thatmay be included in the first set of battery packs 110 are described inU.S. Pat. No. 8,653,787 and U.S. patent application Ser. Nos.13/079,158; 13/475,002; and Ser. No. 13/080,887, which are incorporatedby reference.

The rated voltage of the set of low rated voltage battery packs 20A1generally corresponds to the rated voltage of the set of low ratedvoltage DC power tools 10A1 so that the set of low rated voltage batterypacks 20A1 may supply power to and operate with the low rated voltage DCpower tools 10A1. As described in further detail below, the set of lowrated voltage battery packs 20A1 may also be able to supply power to oneor more of the medium rated voltage DC power tools 10A2, the high ratedvoltage DC power tools 10A3, or the high rated voltage AC/DC power tools10B, for example, by coupling more than one of the low rated voltagebattery packs 20A1 to these tools in series so that the voltage of thelow rated voltage battery packs 20A1 is additive and corresponds to therated voltage of the power tool to which the battery packs are coupled.The low rated voltage battery packs 20A1 may additionally oralternatively be coupled in series with one or more of the medium ratedvoltage battery packs 20A2, the high rated voltage battery packs 20A3,or the convertible battery packs 20A4 to output the desired voltagelevel for any of the medium and high rated voltage DC power tools 10A2,10A3, and/or the AC/DC power tools 10B.

b. Medium Rated Voltage Battery Packs

Referring to FIGS. 1A and 3B, each of the medium rated voltage batterypacks 20A2 includes a DC power tool interface 22A configured to becoupled to a battery pack interface 16A on a corresponding medium ratedvoltage DC power tool 10A2 and to a battery pack interface 16A on acorresponding medium rated voltage battery pack charger 30. The DC powertool interface 22A may include a DC power in/out+ terminal, a DC powerin/out− terminal, and a communications (COMM) terminal. The set ofmedium rated voltage battery packs 20A2 may include one or more batterypacks having a second rated voltage and a second rated capacity. Thesecond rated voltage is, relatively speaking, a medium rated voltage, ascompared to other battery packs in the set of DC battery packs powersupplies 20A. For example, the set of medium rated voltage battery packs20A2 may include battery packs having a rated voltage of 51V-60V (whichmay encompass an advertised voltage of 60V, an operating voltage of51V-57V a nominal voltage of 54V, and a maximum voltage of 60V).However, the set of medium rated voltage battery packs 20A2 is notlimited to a rated voltage of 60V. The set of medium rated voltagebattery packs 20A2 may have other relatively medium rated voltages suchas 40V, 54V, 72V or 80V. Within the set of medium rated voltage batterypacks 20A2, there may be battery packs having the same rated voltage butwith different rated capacities. For example, the set of medium ratedvoltage battery packs 20A2 may include a 60V/1.5 Ah battery pack, a60V/2 Ah battery pack, a 60V/3 Ah battery pack, and/or 60V/4 Ah batterypack. When referring to the medium rated voltage of the set of mediumrated voltage battery packs 20A2, it is meant that the rated voltage ofthe set of medium rated voltage battery packs 20A2 is higher than therated voltage of the set of low rated voltage battery packs 20A1 butlower than the rated voltage of the set of high rated voltage batterypacks 20A3.

The rated voltage of the set of medium rated voltage battery packs 20A2generally corresponds to the rated voltage of the medium rated voltageDC power tools 10A2 so that the set of medium rated voltage batterypacks 20A2 may supply power to and operated with the medium ratedvoltage DC power tools 10A2. As described in further detail below, theset of medium rated voltage battery packs 20A2 may also be able tosupply power to the high rated voltage DC power tools 10A3 or the AC/DCpower tools 10B, for example, by coupling more than one of the mediumrated voltage battery packs 20A2 to these tools other in series so thatthe voltage of the medium rated voltage battery packs 20A2 is additiveand corresponds to the rated voltage of the power tool to which thebattery packs are coupled. The medium rated voltage battery packs 20A2may additionally or alternatively be coupled in series with any of thelow rated voltage battery packs 20A1, the high rated voltage batterypacks 20A3, or the convertible battery packs 20A4 to output the desiredvoltage level for any of the high rated voltage DC power tools 10A orthe AC/DC power tools 10B.

c. High Rated Voltage Battery Packs

Referring to FIGS. 1A and 3C, each of the high rated voltage batterypacks 20A3 includes a DC power tool interface 22A configured to becoupled to a battery pack interface 16A on a corresponding high ratedvoltage DC power tool 10A3 and to a battery pack interface 16A on acorresponding medium rated voltage battery pack charger 30. The DC powertool interface 22A may include a DC power in/out+ terminal, a DC powerin/out− terminal, and a communications (COMM) terminal. The set of highrated voltage battery packs 20A3 may include one or more battery packshaving a third rated voltage and a third rated capacity. The third ratedvoltage is, relatively speaking, a high rated voltage, as compared toother battery packs in the set of DC battery pack power supplies 220A.For example, the set of high rated voltage battery packs 20A3 mayinclude battery packs having a rated voltage of 102V-120V (which mayencompass an advertised voltage of 120V, an operating voltage of102V-114V a nominal voltage of 108V, and maximum voltage of 120V).However, the set of high rated voltage battery packs 20A3 is not limitedto a rated voltage of 120V. The set of high rated voltage battery packs20A3 may have other relatively high rated voltages such as 90V, 100V,110V, or 120V. The high rated voltage of the set of high rated voltagebattery packs 20A3 may alternatively be referred to as an AC ratedvoltage since the high rated voltage may correspond to a rated voltageof an AC mains power supply in the country in which the power tool isoperable and/or sold. Within the set of high rated voltage battery packs20A3, there may be battery packs having the same rated voltage but withdifferent rated capacities. For example, the set of high rated voltagebattery packs 20A3 may include a 120V/1.5 Ah battery pack, a 120V/2 Ahbattery pack, a 120V/3 Ah battery pack, and/or a 120V/4 Ah battery pack.When referring to the high rated voltage of the set of high ratedvoltage battery packs 20A3, it is meant that the rated voltage of theset of high rated voltage battery packs 20A3 is higher than the ratedvoltage of the set of low rated voltage battery packs 20A1 and the ratedvoltage of the set of medium rated voltage battery packs 20A2.

The rated voltage of the set of high rated voltage battery packs 20A3generally corresponds to the rated voltage of the high rated voltage DCpower tools 10A3 and the AC/DC power tools 10E3 so that the set of highrated voltage battery packs 20A3 may supply power to and operate withthe high rated voltage DC power tools 10A3 and the AC/DC power tools10B. As described in further detail below, the set of high rated voltagebattery packs 20A3 may also be able to supply power to the very highrated voltage AC/DC power tools 128, for example, by coupling more thanone of the high rated voltage battery packs 20A3 to the tools in seriesso that the voltage of the high rated voltage battery packs 20A3 isadditive. The high rated voltage battery packs 20A3 may additionally oralternatively be coupled in series with any of the low rated voltagebattery packs 20A1, the medium rated voltage battery packs 20A2, or theconvertible battery packs 20A4 to output the desired voltage level forany of the AC/DC power tools 10B.

d. Convertible Battery Packs

Referring to FIG. 1A and as discussed in greater detail in U.S. Pat. No.9,406,915, which is incorporated herein by reference, the set ofconvertible battery packs 20A4 are convertible battery packs, each ofwhich may be converted between (1) a first rated voltage and a firstrated capacity and (2) a second rated voltage and a second ratedcapacity that are different than the first rated voltage and the firstrated capacity. For example, the configuration of the cells residing inthe battery pack 20A4 may be changed between a first cell configurationthat places the convertible battery pack 20A4 in a first battery packconfiguration and a second cell configuration that places theconvertible battery pack 20A4 in a second battery pack configuration. Inone implementation, in the first battery pack configuration, theconvertible battery pack 20A4 has a low rated voltage and a high ratedcapacity, and in the second battery pack configuration, the battery packhas a medium rated voltage and a low rated capacity. In other words, thebattery packs of the set of convertible battery packs 20A4 are capableof having at least two different rated voltages, e.g., a lower ratedvoltage and a higher rated voltage, and at least two differentcapacities, e.g., a higher rated capacity and a lower rated capacity.

As noted above, low, medium and high ratings are relative terms and arenot intended to limit the battery packs of the set of convertiblebattery packs 20A4 to specific ratings. Instead, the convertible batterypacks of the set of convertible battery packs 20A4 may be able tooperate with the low rated voltage power tools 10A1 and with the mediumrated voltage power tools 20A2, where the medium rated voltage isgreater than the low rated voltage. In one particular embodiment, theconvertible battery packs 20A4 are convertible between a low ratedvoltage (e.g., 17V-20V, which may encompass an advertised voltage of20V, an operating voltage of 17V-19V a nominal voltage of 18V, and amaximum voltage of 20V) that corresponds to the low rated voltage of thelow rated voltage DC power tools 10A1, and a medium rated voltage (e.g.,60V, which may encompass an advertised voltage of 60V, an operatingvoltage of 51V-57V, a nominal voltage of 54V, and a maximum voltage of60V) that corresponds to the medium rated voltage of the medium ratedvoltage DC power tools 10A2. In addition, as described further below,the convertible battery packs 20A4 may be able to supply power to thehigh rated voltage DC power tools 10A3 and the high voltage AC/DC powertools 10B, e.g., with the convertible battery packs 20A4 operating attheir medium rated voltage and connected to each other in series so thattheir voltage is additive to correspond to the rated voltage of the highrated voltage DC power tools 10A3 or the AC/DC power tools 10B.

In other embodiments, the convertible battery packs may be backwardscompatible with a first pre-existing set of power tools having a firstrated voltage when in a first rated voltage configuration and forwardscompatible with a second new set of power tools having a second ratedvoltage. For example, the convertible battery packs may be coupleable toa first set of power tools when in a first rated voltage configuration,where the first set of power tools is an existing power tool that was onsale prior to May 18, 2014, and to a second set of power tools when in asecond rated voltage configuration, where the second set of power toolswas not on sale prior to May 18, 2014. For example, in one possibleimplementation a low/medium rated convertible battery pack may becoupleable in a 20V rated voltage configuration to one or more ofDeWALT® 20V MAX cordless power tools sold by DeWALT Industrial Tool Co.of Towson, Md., that were on sale prior to May 18, 2014, and in a 60Vrated voltage configuration to one or more 60V rated power tools thatwere not on sale prior to May 18, 2014. Thus, the convertible batterypacks facilitate compatibility in a power tool system having bothpre-existing and new sets of power tools.

Referring to FIGS. 1A and 3A-3C, the convertible battery packs 20A4 eachinclude a plurality of cells and a DC power tool interface 22Aconfigured to be coupled to a battery pack interface 16A on acorresponding low, medium, or high rated voltage DC power tool 10A1,10A2, or 10A3. The DC power tool interface 22A is also configured to becoupled the battery pack interface 16A on a corresponding battery packcharger 30. As discussed in greater detail below, the convertiblebattery pack 20A4 may be coupled to one or more rated voltage batterypack chargers 30 where the convertible battery pack 20A4 is placed inthe voltage rating configuration that corresponds to that battery packcharger 30 when it is coupled to that battery pack charger 30. Forexample, the DC power tool interface 22A may include a DC power in/out+terminal, a DC power in/out− terminal, and a communications (COMM)terminal. Several possible embodiments of convertible battery packs andtheir interfaces are described in further detail below.

B. Battery Pack Chargers

Referring to FIGS. 1A, and 3A-3C, the set of battery pack chargers 30contains one more battery pack chargers that are able to mechanicallyand electrically connect to the battery packs of one or more of the lowrated voltage battery packs 20A1, medium rated voltage battery packs20A2, high rated voltage battery packs 20A3, and convertible batterypacks 20A4. The set of battery pack chargers 30 are able to charge anyof the battery packs 20A1, 20A2, 20A3, 20A4. The battery pack chargers30 may have different rated voltages. For example, the battery packchargers 30 may have one or more rated voltages, such as a low ratedvoltage, a medium rated voltage, and/or a high rated voltage to matchthe rated voltages of the sets of battery packs in the system. Thebattery pack chargers 30 may also have multiple or a range of ratedvoltages (e.g., a low-medium rated voltage) to enable the battery packchargers 30 to charge battery packs having different rated voltages. Thebattery pack chargers 30 may also have a battery pack interface 16Aconfigured to be coupled to a DC power tool interface 22A on the batterypacks. The battery pack interface 16A may include a DC power in/out+terminal, a DC power in/out− terminal, and a communications (COMM)terminal. In certain embodiments, the battery pack interface 16A mayinclude a converter configured to cause one of the convertible batterypacks to be placed in a desired rated voltage configuration for chargingthe battery pack, as discussed in greater detail below.

C. Power Tools

1. Low Rated Voltage DC Power Tools

Referring to FIGS. 1A and 3A, the set of low rated voltage power tools10A1 includes one or more different types of cordless or DC-only powertools that utilize DC power supplied from one or more of the DC batterypack power supplies 20A that have a low rated voltage (such as removableand rechargeable battery packs). The rated voltage of the low ratedvoltage DC power tools 10A1 generally correspond to the rated voltage ofthe low rated voltage battery packs 20A1 or to the rated voltage of theconvertible battery packs 20A4 when placed in a low rated voltageconfiguration. For example, the low rated voltage DC power tools 10A1having a rated voltage of 20V may be powered using 20V battery pack(s)20A1 or by 20V/60V convertible battery packs 20A4 in a 20Vconfiguration. The power tool rated voltage of 20V may itself beshorthand for a broader rated voltage of 17-20V, which may encompass anoperating voltage range of, e.g., 17V-20V that encompasses the ratedvoltage range of the low rated voltage battery packs.

The low rated voltage DC power tools 10A1 each include a motor 12A thatcan be powered by a DC-only power supply. The motor 12A may be anybrushed or brushless DC electric motor, including, but not limited to, apermanent magnet brushless DC motor (BLDC), a permanent magnet brushedmotor, a universal motor, etc. The low rated voltage DC power tools 10A1may also include a motor control circuit 14A configured to receive DCpower from a battery pack interface 16A via a DC line input DC+/− and tocontrol power delivery from the DC power supply to the motor 12A. In anexemplary embodiment, the motor control circuit 14A may include a powerunit 18A having one or more power switches (not shown) disposed betweenthe power supply and the motor 12A. The power switch may be anelectro-mechanical on/off switch, a power semiconductor device (e.g.,diode, FET, BJT, IGBT, etc.), or a combination thereof. In an exemplaryembodiment, the motor control circuit 14A may further include a controlunit 11. The control unit 11 may be arranged to control a switchingoperation of the power switches in the power unit 18A. In an exemplaryembodiment, the control unit 11 may include a micro-controller orsimilar programmable module configured to control gates of powerswitches. Additionally or alternatively, the control unit 11 may beconfigured to monitor and manage the operation of the DC battery packpower supplies 20A. Additionally or alternatively, the control unit 11may be configured to monitor and manage various tool operations andconditions, such as temperature control, over-speed control, brakingcontrol, etc.

In an exemplary embodiment, as discussed in greater detail below, thelow rated voltage DC power tool 10A1 may be a constant-speed tool (e.g.,a hand-held light, saw, grinder, etc.). In such a power tool, the powerunit 18A may simply include an electro-mechanical on/off switchengageable by a tool user. Alternatively, the power unit 18A may includeone or more semi-conductor devices controlled by the control unit 11 atfixed no-load speed to turn the tool motor 12A on or off.

In another embodiment, as discussed in greater detail below, a low ratedvoltage DC power tool 10A1 may be a variable-speed tool (e.g., ahand-held drill, impact driver, reciprocating saw, etc.). In such apower tool, the power switches of the power unit 18A may include one ormore semiconductor devices arranged in various configurations (e.g., aFET and a diode, an H-bridge, etc.), and the control unit 11 may controla pulse-width modulation of the power switches to control a speed of themotor 12A.

The low rated voltage DC power tools 10A1 may include hand-held cordlesstools such as drills, circular saws, screwdrivers, reciprocating saws,oscillating tools, impact drivers, and flashlights, among others. Thelow rated voltage power tools may include existing cordless power toolsthat were on sale prior to May 18, 2014. Examples of such low ratedvoltage DC power tools 10A1 may include one or more of the DeWALT® 20VMAX set of cordless power tools sold by DeWALT Industrial Tool Co. ofTowson, Md. The low rated voltage DC power tools 10A1 may alternativelyinclude cordless power tools that were not on sale prior to May 18,2014. In other examples, U.S. Pat. Nos. 8,381,830, 8,317,350, 8,267,192,D646,947, and D644,494, which are incorporated by reference, disclosetools comprising or similar to the low rated voltage cordless powertools 10A1.

2. Medium Rated Voltage DC Power Tools

Referring to FIGS. 1A and 3B, the set of medium rated voltage DC powertools 10A2 may include one or more different types of cordless orDC-only power tools that utilize DC power supplied from one or more ofthe DC battery pack power supplies 20A that alone or together have amedium rated voltage (such as removable and rechargeable battery packs.The rated voltage of the medium rated voltage DC power tools 10A2 willgenerally correspond to the rated voltage of the medium rated voltagebattery packs 20A2 or to the rated voltage of the convertible batterypacks 20A4 when placed in a medium rated voltage configuration. Forexample, the medium rated voltage DC power tools 10A2 may have a ratedvoltage of 60V and may be powered by a 60V medium rated voltage batterypack 20A2 or by a 20V/60V convertible battery pack 20A4 in a 60Vconfiguration. The power tool rated voltage of 60V may be shorthand fora broader rated voltage of 17-20V, which may encompass an operatingrange of, e.g., 51V-60V that encompasses the rated voltage of the mediumrated voltage battery packs. In an exemplary embodiment, the mediumrated voltage DC power tool 10A2 may include multiple battery interfacesconfigured to receive two or more low rated voltage battery packs 20A1.In an exemplary embodiment, the medium rated voltage DC power tool 10A2may additionally include circuitry to couple the DC battery pack powersupplies 20A in series to produce a desired medium rated voltagecorresponding to the rated voltage of the medium rated voltage DC powertool 10A2.

Similar to low rated voltage DC power tools 10A1 discussed above, themedium rated voltage DC power tools 10A2 each include a motor 12A thatcan be powered by a DC battery pack power supply 20A. The motor 12A maybe any brushed or brushless DC electric motor, including, but notlimited to, a permanent magnet brushless DC motor (BLDC), a permanentmagnet brushed motor, a universal motor, etc. The medium rated voltageDC power tools 10A2 also include a motor control circuit 14A configuredto receive DC power from the battery pack interface 16A via a DC lineinput DC+/− and to control power delivery from the DC power supply tothe motor 12A. In an exemplary embodiment, the motor control circuit 14Amay include a power unit 18A having one or more power switches (notshown) disposed between the power supply and the motor 12A. The powerswitch may be an electro-mechanical on/off switch, a power semiconductordevice (e.g., diode, FET, BJT, IGBT, etc.), or a combination thereof. Inan exemplary embodiment, the motor control circuit 14A may furtherinclude a control unit 11. The control unit 11 may be arranged tocontrol a switching operation of the power switches in the power unit18A. Similarly to the motor control circuit 14A described above for lowrated voltage DC power tools 10A1, the motor control circuit 14A maycontrol the motor 12A in fixed or variable speed. In an exemplaryembodiment, the control unit 11 may include a micro-controller orsimilar programmable module configured to control gates of powerswitches. Additionally or alternatively, the control unit 11 may beconfigured to monitor and manage the operation of the DC battery packpower supplies 20A. Additionally or alternatively, the control unit 11may be configured to monitor and manage various tool operations andconditions, such as temperature control, over-speed control, brakingcontrol, etc.

The medium rated voltage DC power tools 10A2 may include similar typesof tools as the low rated voltage DC power tools 10A1 that haverelatively higher power output requirements, such as drills, a circularsaws, screwdrivers, reciprocating saws, oscillating tools, impactdrivers and flashlights. The medium rated voltage DC power tools 10A2may also or alternatively have other types of tools that require higherpower or capacity than the low rated voltage DC power tools 10A1, suchas chainsaws, string trimmers, hedge trimmers, lawn mowers, nailersand/or rotary hammers.

In yet another and/or a further embodiment, as discussed in more detailbelow, the motor control circuit 14A of a medium rated voltage DC powertool 10A2 enables the motor 12A to be powered using DC battery packpower supplies 20A having rated voltages that are different from eachother and that are less than a medium rated voltage. In other words,medium rated voltage DC power tool 10A2 may be configured to operate atmore than one rated voltage (e.g., at a low rated voltage or at a mediumrated voltage). Such a medium rated voltage DC power tool 10A2 may besaid to have more than one voltage rating corresponding to each of thevoltage ratings of the DC power supplies that can power the tool. Forexample, the medium rated voltage DC power tool 10A2 of FIG. 3B may havea low/medium rated voltage (e.g., a 20V/60V rated voltage, 40V/60V ratedvoltage) that is capable of being alternatively powered by one of thelow rated voltage battery packs 20A1 (e.g., a 20V battery pack), by oneof the medium rated voltage battery packs 20A2 (e.g., a 60V batterypack), or by a convertible battery pack 20A4 in either a low ratedvoltage configuration or a medium rated voltage configuration. Inalternative implementations, the medium rated voltage DC power tool 10A2may operate using a pair of low rated voltage battery packs 20A1connected in series to operate at yet another low or medium ratedvoltage that is different than the medium rated voltage of the motor 12Ain the medium rated voltage DC power tool 10A2 (e.g., two low ratedvoltage 18V battery packs 20A1 connected in series to generate acombined low rated voltage of 36V).

Operating the power tool motor 12A at significantly different voltagelevels will yield significant differences in power tool performance, inparticular the rotational speed of the motor, which may be noticeableand in some cases unsatisfactory to the users. Thus, in an embodiment ofthe invention herein described, the motor control circuit 14A isconfigured to optimize the motor 12A performance based on the ratedvoltage of the power supply, i.e., based on whether the medium ratedvoltage DC power tool 10A2 is coupled with either a low rated voltage DCpower supply (e.g., low rated voltage battery pack 20A1) or a mediumrated voltage power supply (e.g., medium rated voltage battery pack 20A2for which the motor 212A in the medium rated voltage DC power tools 10A2is optimized or rated). In doing so, the difference in the tool's outputperformance is minimized, or at least reduced to a level that issatisfactory to the end user.

In this embodiment, the motor control circuit 14A is configured toeither boost or reduce an effective motor performance from the powersupply to a level that corresponds to the operating voltage range (orvoltage rating) of the medium rated voltage DC power tool 10A2. Inparticular, the motor control circuit 14A may reduce the power output ofthe tool 10A when used with a medium rated voltage battery pack 20A2 tomatch (or come reasonably close to) the output level of the tool 10Awhen used with a low rated voltage battery pack 20A1 in a manner that issatisfactory to an end user. Alternatively or additionally, motorcontrol circuit 14A may boost the power output of the medium ratedvoltage DC power tool 10A2 when used with a low rated voltage batterypack 20A1 to match (or come reasonably close to) the output level of themedium rated voltage DC power tool 10A2 when used with a medium ratedvoltage battery pack 20A2 in a manner that is satisfactory to an enduser. In an embodiment, the low/medium rated voltage DC power tool 10A2may be configured to identify the rated voltage of the power supply via,for example, a battery ID, and optimize motor performance accordingly.These methods for optimizing (i.e., boosting or reducing) the effectivemotor performance are discussed later in this disclosure in detail.

3. High Rated Voltage DC Power Tools

Referring to FIGS. 1A and 3C, the set of high rated voltage DC powertools 10A3 may include cordless (DC only) high rated (or AC rated)voltage power tools with motors configured to operate at a high ratedvoltage and high output power (e.g., approximately 1000 to 1500 Watts).Similar to the low and medium rated voltage DC power tools 10A1, 10A2,the high rated voltage DC power tools 10A3 may include various cordlesstools (i.e., power tools, outdoor tools, etc.) for high power outputapplications. The high rated voltage DC power tools 10A3 may include forexample, similar types of tools as the low rated voltage and mediumrated voltage DC power tools, such as drills, circular saws,screwdrivers, reciprocating saws, oscillating tools, impact drivers,flashlights, string trimmers, hedge trimmers, lawn mowers, nailersand/or rotary hammers. The high rated voltage DC power tools may also oralternatively include other types of tools that require higher power orcapacity such as miter saws, chain saws, hammer drills, grinders, andcompressors.

Similar to the low and medium rated voltage DC power tools 10A1, 10A2,the high rated voltage DC power tools 10A3 each include a motor 12A, amotor control circuit 14A, and a battery pack interface 16A that areconfigured to enable operation from one or more DC battery pack powersupplies 20A that together have a high rated voltage that corresponds tothe rated voltage of the power tool 10A. Similarly to motors 12Adescribed above with reference to FIG. 3A, the motor 12A may be anybrushed or brushless DC electric motor, including, but not limited to, apermanent magnet brushless DC motor (BLDC), a permanent magnet DCbrushed motor (PMDC), a universal motor, etc. Similarly to motor controlcircuits 14A may include a power unit 18A having one or more powerswitches (not shown) disposed between the power supply and the motor12A. The power switch may be an electro-mechanical on/off switch, apower semiconductor device (e.g., diode, FET, BJT, IGBT, etc.), or acombination thereof. In an embodiment, the motor control circuit 14A mayfurther include a control unit 11. The control unit 11 may be arrangedto control a switching operation of the power switches in the power unit18A. The motor control circuit 14A may control the motor 12A in fixed orvariable speed. In an embodiment, the control unit 11 may include amicro-controller or similar programmable module configured to controlgates of power switches. Additionally or alternatively, the control unit11 may be configured to monitor and manage the operation of the DCbattery pack power supplies 20A. Additionally or alternatively, thecontrol unit 11 may be configured to monitor and manage various tooloperations and conditions.

Referring to FIG. 3C, the high rated voltage DC power tools 10A3 may bepowered by a single DC battery pack power supply 20A received in abattery pack interface (or battery receptacle) 16A. In an embodiment,the DC battery pack power supply 20A may be a high rated voltage batterypack 20A3 having a high rated voltage (e.g., 120V) that corresponds tothe rated voltage of the high rated voltage DC power tool 10A3.

Referring to FIG. 3C, in an alternative embodiment, the battery packinterface 16A of the high rated voltage DC power tools 10A3 may includetwo or more battery receptacles 16A1, 16A2 that receive two or more DCbattery pack power supplies 20A at a given time. In an embodiment, thehigh rated voltage DC power tools 10A3 may be powered by a pair of DCbattery pack power supplies 20A received together in the batteryreceptacles 216A1, 216A2. In this embodiment, the battery pack interface16A also may include a switching unit (not shown) configured to connectthe two DC battery pack power supplies 20A in series. The switching unitmay for example include a circuit provided within the battery packinterface 16A, or within the motor control circuit 14A. Alternatively,the DC battery pack power supplies 20A may be medium rated voltagebattery packs 20A2 connected in series via the switching unit 120-10 tosimilarly output a high rated voltage (e.g., two 60V battery packsconnected in series for a combined rated voltage of 120V). In yetanother embodiment, a single high rated voltage battery pack 20A3 may becoupled to one of the battery receptacles to provide a rated voltage of120V. For example, the high rated voltage DC power tools 10A2 may have arated voltage of 60V and may be powered by two 60V medium rated voltagebattery packs 20A2 or by two 20V/60V convertible battery packs 20A4 intheir 60V configuration. The power tool rated voltage of 120V may itselfbe shorthand for a broader rated voltage range of 102V-120V, which mayencompass an operating range of, e.g., 102V-120V that encompasses theoperating range of the two medium rated voltage battery packs.

In an embodiment, the total rated voltage of the battery packs receivedin the cordless power tool battery receptacle(s) 16A may correspond tothe rated voltage of the cordless DC power tool 10A itself. However, inother embodiments, the high rated voltage cordless DC power tool 10A3may additionally be operable using one or more DC battery pack powersupplies 20A that together have a rated voltage that is lower than therated voltage of the motor 12A and the motor control circuit 14A in thehigh rated cordless DC power tool 10A3. In this latter case, thecordless DC power tool 10A may be said to have multiple rated voltagescorresponding to the rated voltages of the DC battery pack powersupplies 20A that the high rated voltage DC power tool 10A3 will accept.For example, the high rated voltage DC power tool 10A3 may be amedium/high rated voltage DC power tool if it is able to operate usingeither a high rated voltage battery pack 20A3 or a medium rated voltagebattery pack 20A2 (e.g., a 60V/120V, a 60-120V power tool, a 80V/120V,or a 80-120V power tool) that is capable of being alternatively poweredby a plurality of low rated voltage battery packs 20A1 (e.g., a 20Vbattery packs), one or more medium rated voltage battery packs 20A2(e.g., a 60V battery pack), one high rated voltage battery pack 20A3, orone or more convertible battery packs 20A4. The user may mix and matchany of the DC battery pack power supplies 20A for use with the highrated voltage DC power tool 10A3.

In order for the motor in the high rated voltage DC power tool 10A3(which as discussed may be optimized to work at a high power and a highvoltage rating) to work acceptably with DC power supplies having a totalvoltage rating that is less than the voltage rating of the motor), themotor control circuit 14A may be configured to optimize the motorperformance based on the rated voltage of the low rated voltage DCbattery packs 20A1. As discussed briefly above and in detail later inthis disclosure, this may be done by optimizing (i.e., booting orreducing) an effective motor performance from the power supply to alevel that corresponds to the operating voltage range (or voltagerating) of the high rated voltage DC power tool 10A3.

In an alternative or additional embodiment (not shown), an AC/DC adaptormay be provided that couples an AC power supply to the battery packinterface 16A and converts the AC power from the AC power supply to a DCsignal of comparable rated voltage to supply a high rated voltage DCpower supply to the high rated voltage DC power tool 10A3 via thebattery pack interface 16A.

4. High (AC) Rated Voltage AC/DC Power Tools

Referring to FIGS. 1A and 4, the corded/cordless (AC/DC) power tools 10Beach have an AC/DC power supply interface 16 with DC line inputsDC+/−(16A), AC line inputs ACH, ACL (16B), and a communications line(COMM) coupled to a motor control circuit 14B. The AC/DC power supplyinterface 16 is configured to be coupled to a tool interface of one ormore of the DC battery pack power supplies 20A and the AC power supplies20B. The DC battery pack power supplies 20A may have a DC power in/out+terminal, a DC power in/out− terminal, and a communications (COMM)terminal that can be coupled to the DC+/− line inputs and thecommunications line (COMM) in the AC/DC power supply interface 16 in theAC/DC power tool 10B. The DC power in/out+ terminal, the DC powerin/out− terminal, and the communications (COMM) terminals of the DCbattery pack power supplies 20A may also be able to couple the DCbattery pack power supplies 20A to the battery pack interfaces 16A ofthe battery pack chargers 30, as described above. The AC power supplies20B may be coupled to the ACH, ACL, and/or the communications (COMM)terminals of the power supply interface 16B in the AC/DC power tool 10Bby AC power H and AC power L terminals or lines and by a communications(COMM) terminal or line. In each AC/DC power tool 10B, the motor controlcircuit 14B and the motor 12B are designed to optimize performance ofthe motor for a given rated voltage of the power tool and of the powersupplies.

As discussed further below, the motors 12B may be brushed motors orbrushless motors, such as a permanent magnet brushless DC motor (BLDC),a permanent magnet DC brushed motor (PMDC), or a universal motor. Themotor control circuit 14B may enable either constant-speed operation orvariable-speed operation, and depending on the type of motor and speedcontrol, may include different power switching and control circuitry, asdescribed in greater detail below.

In an exemplary embodiment, the AC/DC power supply interface 16 may beconfigured to include a single battery pack interface (e.g. a batterypack receptacle) 16A and an AC power interface 16B (e.g. AC power cablereceived in the tool housing). The motor control circuit 14B in thisembodiment may be configured to selectively switch between the AC powersupply 20B and DC battery pack power supply 20A. In this embodiment, theDC battery pack power supply 20A may be a high rated voltage batterypack 20A3 having a high rated voltage (e.g., 120V) that corresponds tothe rated voltage of the AC/DC power tool 10B and/or the rated voltageof the AC power supply 20B. The motor control unit 14B may be configuredto, for example, supply AC power from the AC supply 20B by default whenit senses a current from the AC supply 20B, and otherwise supply powerfrom the DC battery pack power supply 20A.

In another exemplary embodiment, the AC/DC power supply interface 16 maybe configured to include, in addition to the AC supply interface 16B, apair of battery interfaces such as two battery receptacles. Reference ismade herein once again to FIGS. 114-117 of U.S. Pat. No. 9,406,915,which is incorporated herein by reference, for an example of such anarrangement. This arrangement allows the AC/DC power tool 10B to bepowered by more than one DC battery pack power supply 20A that, whenconnected in series, together have a high rated voltage that correspondsto the AC rated voltage of the mains power supply. In this embodiment,the AC/DC power tools 10B may be powered by a pair of the DC batterypack power supplies 20A received in the battery receptacles 16A1, 16A2.In an embodiment, a switching unit may be provided and configured toconnect the two DC battery pack power supplies 20A in series. Such aswitching unit may for example include a simple wire connection providedin AC/DC power supply interface 16 connecting the battery receptacles.Alternatively, such a switching unit may be provided as a part of themotor control circuit 14B.

In this embodiment, the DC battery pack power supplies 20A may be two ofthe medium rated voltage battery packs 20A2 connected in series via aswitching unit to similarly output a high rated voltage (e.g., two 60Vbattery packs connected in series for a combined rated voltage of 120V).Referring to FIG. 116, in yet another exemplary embodiment, a singlehigh rated voltage battery pack 20A3 may be coupled to one of thebattery receptacles 16A2 to provide a rated voltage of 120V, and theother battery receptacle 16A1 may be left unused. In this embodiment,motor control circuit 14B may be configured to select one of the ACpower supply 20B or the combined DC battery pack power supplies 20A forsupplying power to the motor 12B.

In these embodiments, the total rated voltage of the DC battery packpower supplies 20A received in the AC/DC power tool battery packreceptacle(s) 16A may correspond to the rated voltage level of the AC/DCpower tool 10B, which generally corresponds to the rated voltage of theAC mains power supply 20B. As previously discussed, the power supply 20used for the high rated voltage DC power tools 10A3 or the AC/DC powertools 10B is a high rated voltage mains AC power supply 20B. Forexample, the AC/DC power tools 10A2 may have a rated voltage of 120V andmay be able to be powered by a 120 VAC AC mains power supply or by two20V/60V convertible battery packs 20A4 in their 60V configuration andconnected in series. The power tool rated voltage of 120V may beshorthand for a broader rated voltage of, e.g., 100V-120V thatencompasses the operating range of the power tool and the operatingrange of the two medium rated voltage battery packs. In oneimplementation, the power tool rated voltage of 120V may be shorthandfor an even broader operating range of 90V-132V which encompasses theentire operating range of the two medium rated voltage battery packs(e.g., 102 VDC-120 VDC) and the all of the AC power supplies availablein North America and Japan (e.g., 100 VAC, 110 VAC, 120 VAC) with a ±10%error factor to account for variances in the voltage of the AC mainspower supplies).

In other embodiments, the AC/DC power tools 10B may additionally beoperable using one or more of the DC battery pack power supplies 20Athat together have a rated voltage that is lower than the AC ratedvoltage of the AC mains power supply, and that is less than the voltagerating of the motor 12A and motor control circuit 14A. In thisembodiment, the AC/DC power tool 10B may be said to have multiple ratedvoltages corresponding to the rated voltages of the DC battery packpower supplies 20A and the AC power supply 20B that the AC/DC power tool10B will accept. For example, the AC/DC power tool 10B is be amedium/high rated power tool if it is able to operate using either amedium rated voltage battery pack 20A2 or a high rated voltage AC powersupply 20B (e.g., a 60V/120V or a 60-120V or 60 VDC/120 VAC). Accordingto this embodiment, the user may be given the ability to mix and matchany of the DC battery pack power supplies 20A for use with AC/DC powertool 10B. For example, AC/DC power tool 10B may be able to be used withtwo low rated voltage packs 20A1 (e.g., 20V, 30V, or 40V packs)connected in series via a switching unit to output a rated voltage ofbetween 40V to 80V. In another example, the AC/DC power tool 10B may beused with a low rated voltage battery pack 20A1 and a medium ratedvoltage battery pack 20A2 for a total rated voltage of between 80V to100V.

In order for the motor 12B in the AC/DC power tool 10B (which asdiscussed above is optimized to work at a high output power and a highvoltage rating) to work acceptably with DC battery pack power supplieshaving a total voltage rating that is less than the high voltage ratingof the tool (e.g., in the range of 40V to 100V as discussed above), themotor control circuit 14B may be configured to optimize the motorperformance based on the rated voltage of the DC battery pack powersupplies 20A. As discussed briefly above and in detail later in thisdisclosure, this may be done by optimizing (i.e., boosting or reducing)an effective motor performance from the power supply to a level thatcorresponds to the operating voltage range (or voltage rating) of thehigh rated voltage DC power tool 10A3.

II. AC/DC Power Tools and Motor Controls

Referring to FIGS. 1A and 5A, the high rated voltage AC/DC power tools10B may be classified based on the type of motor, i.e., high ratedvoltage AC/DC power tools with brushed motors 122 and high rated voltageAC/DC power tools with brushless motors 128. Referring also to FIG. 5B,the AC rated voltage AC/DC power tools with brushed motors 122 may befurther classified into four subsets based on speed control and motortype: constant-speed AC/DC power tools with universal motors 123,variable-speed AC/DC power tools with universal motors 124,constant-speed AC/DC power tools with DC brushed motors 125, andvariable-speed AC/DC power tools with universal motors 126. Thesevarious sets and subsets of high rated voltage AC/DC power tools arediscussed in greater detail below.

In the ensuing FIGS. 5A-15E, power tools 123, 124, 125, 126 and 128 mayeach correspond to power tool 10B depicted in FIG. 4. Similarly, in theensuing FIGS. 5A-15E, motors 123-2, 124-2, 125-2, 126-2, and 202 mayeach correspond to motor 12B in FIG. 4; motor control circuits 123-4,124-4, 125-4, 126-4, and 204 may each correspond to motor controlcircuit 14B in FIG. 4; power units 123-6, 124-6, 125-6, 126-6, and 206may each correspond to power unit 18B in FIG. 4; control unit 123-8,124-8, 125-8, 126-8, and 208 may each correspond to control unit 11B inFIG. 4; and power supply interfaces 123-5, 124-5, 125-5, 126-5, and128-5 may each correspond to power supply interface 16B in FIG. 4.

A. Constant-Speed AC/DC Power Tools with Universal Motors

Turning now to FIGS. 6A-6D, the first subset of AC/DC power tools withbrushed motors 122 includes the constant-speed AC/DC power tools 123with universal motors (herein referred to as constant-speeduniversal-motor tools 123). These include corded/cordless (AC/DC) powertools that operate at constant speed at no load (or constant load) andinclude brushed universal motors 123-2 configured to operate at a highrated voltage (e.g., 100V to 120V, or more broadly 90V to 132V) and highpower (e.g., 1500 to 2500 Watts). A universal motor is a series-woundmotor having stator field coils and a commutator connected to the fieldcoils in series. A universal motor in this manner can work with a DCpower supply as well as an AC power supply. In an embodiment,constant-speed universal motor tools 123 may include high powered toolsfor high power applications such as concrete hammers, miter saws, tablesaws, vacuums, blowers, and lawn mowers, etc.

In an embodiment, a constant-speed universal motor tool 123 includes amotor control circuit 123-4 that operates the universal motor 123-2 at aconstant speed under no load. The power tool 123 further includes powersupply interface 123-5 arranged to receive power from one or more of theaforementioned DC power supplies and/or AC power supplies. The powersupply interface 123-5 is electrically coupled to the motor controlcircuit 123-4 by DC power lines DC+ and DC− (for delivering power from aDC power supply) and by AC power lines ACH and ACL (for delivering powerfrom an AC power supply).

In an embodiment, motor control circuit 123-4 may include a power unit123-6. In an embodiment, power unit 123-6 includes an electro-mechanicalON/OFF switch 123-12. In an embodiment, the tool 123 includes an ON/OFFtrigger or actuator (not shown) coupled to ON/OFF switch 123-12 enablingthe user to turn the motor 123-2 ON or OFF. The ON/OFF switch 123-12 isprovided in series with the power supply to electrically connect ordisconnect supply of power from power supply interface 123-5 to themotor 123-2.

Referring to FIG. 6A, constant-speed universal motor tool 123 isdepicted according to one embodiment, where the ACH and DC+ power linesare coupled together at common positive node 123-11 a, and the ACL andDC− power lines are coupled together at a common negative node 123-11 b.In this embodiment, ON/OFF switch 123-12 is arranged between thepositive common node 123-11 a and the motor 123-2. To ensure that onlyone of the AC or DC power supplies are utilized at any given time, in anembodiment, a mechanical lockout may be utilized. In an exemplaryembodiment, the mechanical lockout may physically block access to theone of the AC or DC power supplies at any given time.

In addition, as depicted in FIG. 6A, constant-speed universal motor tool123 may be further provided with a control unit 123-8. In an embodiment,control unit 123-8 may be coupled to a power switch 123-13 that isarranged inside power unit 123-6 between the DC+ power line of powersupply interface 123-5 and the ON/OFF switch 123-12. In an embodiment,control unit 123-8 may be provided to monitor the power tool 123 and/orbattery conditions. In an embodiment, control unit 123-8 may be coupledto tool 123 elements such as a thermistor inside a tool. In anembodiment, control unit 123-8 may also be coupled to the batterypack(s) via a communication signal line COMM provided from power supplyinterface 123-5. The COMM signal line may provide a control orinformational signal relating to the operation or condition of thebattery pack(s) to the control unit 123-8. In an embodiment, controlunit 123-8 may be configured to cut off power from the DC+ power linefrom power supply interface 123-5 using the power switch 123-13 if toolfault conditions (e.g., tool over-temperature, tool over-current, etc.)or battery fault conditions (e.g., battery over-temperature, batteryover-current, battery over-voltage, battery under-voltage, etc.) aredetected. In an embodiment, power switch 123-13 may include a FET orother controllable switch that is controlled by control unit 123-8.

FIG. 6B-6D depict the constant-speed universal motor tool 123 accordingto an alternative embodiment, where the DC power lines DC+/DC- and ACpower lines ACH/ACL are isolated via a power supply switching unit123-15 to ensure that power cannot be supplied from both the AC powersupply and the DC power supply at the same time (even if the powersupply interface 123-5 is coupled to both AC and DC power supplies).

In one embodiment, as shown in FIG. 6B, the power supply switching unit123-15 may include a normally-closed single-pole, single-throw relayarranged between the DC power line DC+ and the ON/OFF switch 123-12,with a coil coupled to the AC power line ACH and ACL. The output of thepower supply switching unit 123-15 and the ACH power line are jointlycoupled to the power switch 123-13. When no AC power is being supplied,the relay is inactive, and DC power line DC+ is coupled to the powerswitch 123-13. When AC power is being supplied, the coil is energizedand the relay becomes active, thus disconnecting the DC power line DC+from the power switch 123-13.

In an alternative or additional embodiment, as shown in FIG. 6C, thepower supply switching unit 123-15 may include a double-pole,double-throw switch 123-16 having input terminals coupled to the DC+ andACH power lines of the power supply interface 123-5, and outputterminals jointly coupled to the power switch 123-13. In an embodiment,a second double-pole, double-throw switch 123-17 is provided havinginput terminals coupled to negative DC- and ACL power lines of the powersupply interface 123-5, and output terminals jointly coupled to anegative terminal of the motor 123-2. In an embodiment, switches 123-16and 123-17 may be controlled via a relay coil similar to FIG. 6B.Alternatively, switches 123-16 and 123-17 may be controlled via amechanical switching mechanism (e.g., a moving contact provided on thebattery receptacle that closes the switches when a battery pack isinserted into the battery receptacle).

In another embodiment, as shown in FIG. 6D, the power supply switchingunit 123-15 may include a single-pole, double-throw switch 123-18 havinginput terminals coupled to DC+ and ACH power lines of the power supplyinterface 123-5, and an output terminal coupled to the power switch123-13. In an embodiment, a second single-pole, double-throw switch123-19 is provided having input terminals coupled to negative DC- andACL power lines of the power supply interface 123-5, and an outputterminal coupled to a negative terminal of the motor 123-2. In anembodiment, switches 123-18 and 123-19 may be controlled via a relaycoil similar to FIG. 6B. Alternatively, switches 123-18 and 123-19 maybe controlled via a mechanical switching mechanism (e.g., a movingcontact provided on the battery receptacle that closes the switches whena battery pack is inserted into the battery receptacle).

It must be understood that while tool 123 in FIGS. 6A-6D is providedwith a control unit 123-8 and power switch 123-13 to cut off supply ofpower in an event of a tool or battery fault condition, tool 123 may beprovided without a control unit 123-8 and a power switch 123-13. Forexample, the battery pack(s) may be provided with its own controller tomonitor its fault conditions and manage its operations.

1. Constant-Speed Universal Motor Tools with Power Supplies HavingComparable Voltage Ratings

In FIGS. 6A-6D described above, power tools 123 are designed to operateat a high-rated voltage range of, for example, 100V to 120V (whichcorresponds to the AC power voltage range of 100 VAC to 120 VAC in NorthAmerica and Japan), or more broadly, 90V to 132V (which is ±10% of theAC power voltage range of 100 to 120 VAC), and at high power (e.g., 1500to 2500 Watts). Specifically, the motor 123-2 and power unit 123-6components of power tools 123 are designed and optimized to handlehigh-rated voltage of 100 to 120V, or more broadly 90V to 132V. This maybe done by selecting voltage-compatible power devices, and designing themotor with the appropriate size and winding configuration to handle thehigh-rated voltage range. The motor 123-2 also has an operating voltageor operating voltage range that may be equivalent to, fall within, orcorrespond to the operating voltage or the operating voltage range ofthe tool 123.

In an embodiment, the power supply interface 123-5 is arranged toprovide AC power line having a nominal voltage in the range of 100 to120V (e.g., 120 VAC at 50-60 Hz in the US, or 100 VAC in Japan) from anAC power supply, or a DC power line having a nominal voltage in therange of 100 to 120V (e.g., 108 VDC) from a DC power supply. In otherwords, the DC nominal voltage and the AC nominal voltage providedthrough the power supply interface 123-5 both correspond to (e.g.,match, overlap with, or fall within) the operating voltage range of themotor 123-2 (i.e., high-rated voltage 100V to 120V, or more broadlyapproximately 90V to 132V). It is noted that a nominal voltage of 120VAC corresponds to an average voltage of approximately 108V whenmeasured over the positive half cycles of the AC sinusoidal waveform,which provides an equivalent speed performance as 108 VDC power.

2. Constant-Speed Universal Motor Tools with Power Supplies HavingDisparate Voltage Ratings

FIG. 6E depicts a power tool 123, according to another embodiment of theinvention, where supply of power provided by the AC power supply has anominal voltage that is significantly different from a nominal voltageprovided from the DC power supply. For example, the AC power line of thepower supply interface 123-5 may provide a nominal voltage in the rangeof 100 to 120V, and the DC power line may provide a nominal voltage inthe range of 60V-100V (e.g., 72 VDC or 90 VDC). In another example, theAC power line may provide a nominal voltage in the range of 220 to 240V(e.g., 230V in many European countries or 220V in many Africancountries), and the DC power line may provide a nominal voltage in therange of 100-120V (e.g., 108 VDC).

Operating the power tool motor 123-2 at significantly different voltagelevels may yield significant differences in power tool performance, inparticular the rotational speed of the motor, which may be noticeableand in some cases unsatisfactory to the users. Also supplying voltagelevels outside the operating voltage range of the motor 123-2 may damagethe motor and the associated switching components. Thus, in anembodiment of the invention herein described, the motor control circuit123-4 is configured to optimize a supply of power to the motor (and thusmotor performance) 123-2 depending on the nominal voltage of the AC orDC power lines such that motor 123-2 yields substantially uniform speedand power performance in a manner satisfactory to the end user,regardless of the nominal voltage provided on the AC or DC power lines.

In this embodiment, motor 123-2 may be designed and configured tooperate at a voltage range that encompasses the nominal voltage of theDC power line. In an exemplary embodiment, power tool 123 may bedesigned to operate at a voltage range of for example 60V to 90V (ormore broadly ±10% at 54V to 99V) encompassing the nominal voltage of theDC power line of the power supply interface 123-5 (e.g., 72 VDC or 90VDC), but lower than the nominal voltage of the AC power line (e.g.,220V-240V). In another exemplary embodiment, the motor 123-2 may bedesigned to operate at a voltage range of 100V to 120V (or more broadly±10% at 90V to 132V), encompassing the nominal voltage of the DC powerline of the power supply interface 123-5 (e.g., 108 VDC), but lower thanthe nominal voltage range of 220-240V of the AC power line.

In an embodiment, in order for tool 123 to operate with the highernominal voltage of the AC power line, tool 123 is further provided witha phase-controlled AC switch 123-16. In an embodiment, AC switch 123-16may include a triac or an SRC switch controlled by the control unit123-8. In an embodiment, the control unit 123-8 may be configured to seta fixed conduction band (or firing angle) of the AC switch 123-16corresponding to the operating voltage of the tool 123.

For example, for a tool 123 having a motor 123-2 with an operatingvoltage range of 60V to 100V but receiving AC power having a nominalvoltage of 100V-120V, the conduction band of the AC switch 123-16 may beset to a value in the range of 100 to 140 degrees, e.g., approximately120 degrees. In this example, the firing angle of the AC switch 123-16may be set to 60 degrees. By setting the firing angle to approximately60 degrees, the AC voltage supplied to the motor will be approximatelyin the range of 70-90V, which corresponds to the operating voltage ofthe tool 123. In this manner, the control unit 123-8 optimizing thesupply of power to the motor 123-2.

In another example, for a tool 123 having a motor 123-2 with anoperating voltage range of 100 to 120V but receiving AC power having anominal voltage of 220-240V, the conduction band of the AC switch 123-16may be set to a value in the range of 70 to 110 degrees, e.g.,approximately 90 degrees. In this example, the firing angle of the ACswitch 123-16 may be set to 90 degrees. By setting the firing angle to90 degrees, the AC voltage supplied to the motor will be approximatelyin the range of 100-120V, which corresponds to the operating voltage ofthe tool 123.

In this manner, motor control circuit 123-4 optimizes a supply of powerto the motor 123-2 depending on the nominal voltage of the AC or DCpower lines such that motor 123-2 yields substantially uniform speed andpower performance in a manner satisfactory to the end user, regardlessof the nominal voltage provided on the AC or DC power lines.

B. Variable-Speed AC/DC Power Tools with Universal Motors

Turning now to FIG. 7A-7H, the second subset of AC/DC power tools withbrushed motors 122 includes variable-speed AC/DC power tools 124 withuniversal motors (herein also referred to as variable-speeduniversal-motor tools 124). These include corded/cordless (AC/DC) powertools that operate at variable speed at no load and include brusheduniversal motors 124-2 configured to operate at a high rated voltage(e.g., 100V to 120V, more broadly 90V to 132V) and high power (e.g.,1500 to 2500 Watts). As discussed above, a universal motor isseries-wound motor having stator field coils and a commutator connectedto the field coils in series. A universal motor in this manner can workwith a DC power supply as well as an AC power supply. In an embodiment,variable-speed universal-motor tools 124 may include high-power toolshaving variable speed control, such as concrete drills, hammers,grinders, saws, etc.

In an embodiment, variable-speed universal-motor tool 124 is providedwith a variable-speed actuator (not shown), e.g., a trigger switch, atouch-sense switch, a capacitive switch, a gyroscope, or othervariable-speed input mechanism (not shown) engageable by a user. In anembodiment, the variable-speed actuator is coupled to or includes apotentiometer or other circuitry for generating a variable-speed signal(e.g., variable voltage signal, variable current signal, etc.)indicative of the desired speed of the motor 124-2. In an embodiment,variable-speed universal-motor tool 124 may be additionally providedwith an ON/OFF trigger or actuator (not shown) enabling the user tostart the motor 124-2. Alternatively, the ON/OFF trigger functionallymay be incorporated into the variable-speed actuator (i.e., no separateON/OFF actuator) such that an initial actuation of the variable-speedtrigger by the user acts to start the motor 124-2.

In an embodiment, a variable-speed universal motor tool 124 includes amotor control circuit 124-4 that operates the universal motor 124-2 at avariable speed under no load or constant load. The power tool 124further includes power supply interface 124-5 arranged to receive powerfrom one or more of the aforementioned DC power supplies and/or AC powersupplies. The power supply interface 124-5 is electrically coupled tothe motor control circuit 124-4 by DC power lines DC+ and DC− (fordelivering power from a DC power supply) and by AC power lines ACH andACL (for delivering power from an AC power supply).

In an embodiment, motor control circuit 124-4 may include a power unit124-6. In an embodiment, power unit 124-6 may include a DC switchcircuit 124-14 arranged between the DC power lines DC+/DC- and the motor124-2, and an AC switch 124-16 arranged between the AC power linesACH/ACL and the motor 124-2. In an embodiment, DC switch circuit 124-14may include a combination of one or more power semiconductor devices(e.g., diode, FET, BJT, IGBT, etc.) arranged to switchably provide powerfrom the DC power lines DC+/DC− to the motor 124-2. In an embodiment, ACswitch 124-16 may include a phase-controlled AC switch (e.g., triac,SCR, thyristor, etc.) arranged to switchably provide power from the ACpower lines ACH/ACL to the motor 124-2.

In an embodiment, motor control circuit 124-4 may further include acontrol unit 124-8. Control unit 124-8 may be arranged to control aswitching operation of the DC switch circuit 124-14 and AC switch124-16. In an embodiment, control unit 124-8 may include amicro-controller or similar programmable module configured to controlgates of power switches. In an embodiment, the control unit 124-8 isconfigured to control a PWM duty cycle of one or more semiconductorswitches in the DC switch circuit 124-14 in order to control the speedof the motor 124-2 based on the speed signal from the variable-speedactuator when power is being supplied from one or more battery packsthrough the DC power lines DC+/DC−. Similarly, the control unit 124-8 isconfigured to control a firing angle (or conduction angle) of AC switch124-16 in order to control the speed of the motor 124-2 based on thespeed signal from the variable-speed actuator when power is beingsupplied from the AC power supply through the AC power lines ACH/ACL.

In an embodiment, control unit 124-8 may also be coupled to the batterypack(s) via a communication signal line COMM provided from power supplyinterface 124-5. The COMM signal line may provide a control orinformational signal relating to the operation or condition of thebattery pack(s) to the control unit 124-8. In an embodiment, controlunit 124-8 may be configured to cut off power from the DC output line ofpower supply interface 124-5 using DC switch circuit 124-14 if batteryfault conditions (e.g., battery over-temperature, battery over-current,battery over-voltage, battery under-voltage, etc.) are detected. Controlunit 124-8 may further be configured to cut off power from either the ACor DC output lines of power supply interface 124-5 using DC switchcircuit 124-14 and/or AC switch 124-16 if tool fault conditions (e.g.,tool over-temperature, tool over-current, etc.) are detected.

In an embodiment, power unit 124-6 may be further provided with anelectro-mechanical ON/OFF switch 124-12 coupled to the ON/OFF trigger oractuator discussed above. The ON/OFF switch simply connects ordisconnects supply of power from the power supply interface 124-5 to themotor 124-2. Alternatively, the control unit 124-8 may be configured todeactivate DC switch circuit 124-14 and AC switch 124-16 until itdetects a user actuation of the ON/OFF trigger or actuator (or initialactuator of the variable-speed actuator if ON/OFF trigger functionallyis be incorporated into the variable-speed actuator). The control unit124-8 may then begin operating the motor 124-2 via either the DC switchcircuit 124-14 or AC switch 124-16. In this manner, power unit 124-6 maybe operable without an electro-mechanical ON/OFF switch 124-12.

Referring to FIG. 7A, the variable-speed universal motor tool 124 isdepicted according to one embodiment, where the ACH and DC+ power linesare coupled together at common positive node 124-11 a, and the ACL andDC− power lines are coupled together at a common negative node 124-11 b.In this embodiment, ON/OFF switch 124-12 is arranged between thepositive common node 124-11 a and the motor 124-2. To ensure that onlyone of the AC or DC power supplies are utilized at any given time, in anembodiment, the control unit 124-8 may be configured to activate onlyone of the DC switch circuit 124-14 and AC switch 124-16 at any giventime.

In a further embodiment, as a redundancy measure and to minimizeelectrical leakage, a mechanical lockout may be utilized. In anexemplary embodiment, the mechanical lockout may physically block accessto the AC or DC power supplies at any given time.

FIG. 7B depicts the variable-speed universal motor tool 124 is depictedaccording to an alternative embodiment, where DC power lines DC+/DC- andAC power lines ACH/ACL are isolated via a power supply switching unit124-15 to ensure that power cannot be supplied from both the AC powersupply and the DC power supply at the same time (even if the powersupply interface 124-5 is coupled to both AC and DC power supplies).Switching unit 124-15 may be configured to include relays, single-poledouble-throw switches, double-pole double-throw switches, or acombination thereof, as shown and described with reference to FIGS. 6Bto 6D. It should be understood that while the power supply switchingunit 124-15 in FIG. 7B is depicted between the power supply interface124-5 on one side, and the DC switch circuit 124-14 and AC switch 124-16on the other side, the power supply switching unit 124-15 mayalternatively be provided between the DC switch circuit 124-14 and ACswitch 124-16 on one side, and the motor 124-2 on the other side,depending on the switching arrangement utilized in the power supplyswitching unit 124-15.

As discussed above, DC switch circuit 124-14 may include a combinationof one or more semiconductor devices. FIGS. 7C to 7E depict variousarrangements and embodiments of the DC switch circuit 124-14. In oneembodiment shown in FIG. 7C, a combination of a FET and a diode is usedin what is known as a chopper circuit, and the control unit 124-8 drivesthe gate of the FET (via a gate driver that is not shown) to control aPWM duty cycle of the motor 124-2. In another embodiment, as shown inFIG. 7D, a combination of two FETs is used in series (i.e., ahalf-bridge). The control unit 124-8 may in this case drive the gates orone or both FETs (i.e., single-switch PWM control or PWM control withsynchronous rectification). In yet another embodiment, as shown in FIG.7E, a combination of four FETs is used as an H-bridge (full-bridge). Thecontrol unit 124-8 may in this case drive the gates or two or four FETs(i.e., without or with synchronous rectification) from 0% to 100% PWMduty cycle correlating to the desired speed of the motor from zero tofull speed. It is noted that any type of controllable semiconductordevice such as a BJT, IGBT, etc. may be used in place of the FETs shownin these figures. For a detailed description of these circuits and theassociated PWM control mechanisms, reference is made to U.S. Pat. No.8,446,120 titled: “Electronic Switch Module for a Power Tool,” which isincorporated herein by reference in its entirety.

Referring again to FIGS. 7A and 7B, AC switch 124-16 may include aphase-controlled AC power switch such as a triac, a SCR, a thyristor,etc. arranged in series on AC power line ACH and/or AC power line ACL.In an embodiment, the control unit 124-8 controls the speed of the motorby switching the motor current on and off at periodic intervals inrelation to the zero crossing of the AC current or voltage waveform. Thecontrol unit 124-8 may fire the AC switch 124-16 at a conduction angleof between 0 to 180 degrees within each AC half cycle correlating to thedesired speed of the motor from zero to full speed. For example, if thedesired motor speed is 50% of the full speed, control unit 124-8 mayfire the AC switch 124-16 at 90 degrees, which is the medium point ofthe half cycle. Preferably such periodic intervals are caused to occurin synchronism with the original AC waveform. The conduction angledetermines the point within the AC waveform at which the AC switch124-16 is fired, i.e. turned on, thereby delivering electrical energy tothe motor 124-2. The AC switch 124-16 turns off at the conclusion of theselected period, i.e., at the zero-crossing of the AC waveform. Thus,the conduction angle is measured from the point of firing of AC switch124-16 to the zero-crossing. For a detailed description of phase controlof a triac or other phase controlled AC switch in a power tool,reference is made to U.S. Pat. No. 8,657,031, titled “Universal ControlModule,” U.S. Pat. No. 7,834,566, titled: “Generic Motor Control,” andU.S. Pat. No. 5,986,417, titled: “Sensorless Universal Motor SpeedController,” each of which are incorporated herein by reference in itsentirety.

As discussed, control unit 124-8 controls the switching operation ofboth DC switch circuit 124-14 and AC switch 124-16. When tool 124 iscoupled to an AC power supply, the control unit 124-8 may sense currentthrough the AC power lines ACH/ACL and set its mode of operation tocontrol the AC switch 124-16. In an embodiment, when tool 124 is coupledto a DC power supply, the control unit 124-8 may sense lack of zerocrossing on the AC power lines ACH/ACL and change its mode of operationto control the DC switch circuit 124-14. It is noted that control unit124-8 may set its mode of operation in a variety of ways, e.g., bysensing a signal from the COMM signal line, by sensing voltage on the DCpower lines DC+/DC−, etc.

1. Integrated Power Switch/Diode Bridge

Referring now to FIGS. 7F-7H, variable-speed universal-motor tool 124 isdepicted according to an alternative embodiment, where the AC and DCpower lines of the power supply interface 124-5 are coupled to anintegrated AC/DC power switching circuit 124-18.

As shown in FIGS. 7G and 7H, integrated AC/DC power switching circuit124-18 includes a semiconductor switch Q1 nested within a diode bridgeconfigured out of diodes D1-D4. Semiconductor switch Q1 may be a fieldeffect transistor (FET) as shown in FIG. 7H, or an insulated gatebipolar transistor (IGBT) as shown in FIG. 7G. The semiconductor switchQ1 is arranged between D1 and D3 on one end and between D2 and D4 on theother end. Line inputs DC+ and ACH are jointly coupled to a node of thediode bridge between D1 and D4. The positive motor terminal M+ iscoupled to a node of the diode bridge between D2 and D3.

When tool 124 is coupled to a DC power supply, in an embodiment, thecontrol unit 124-8 sets its mode of operation to DC mode, as discussedabove. In this mode, control unit 124-8 controls the semiconductorswitch Q1 via a PWM technique to control motor speed, i.e., by turningswitch Q1 ON and OFF to provide a pulse voltage. The PWM duty cycle, orratio of the ON and OFF periods in the PWM signal, is selected accordingto the desired speed of the motor.

When tool 124 is coupled to an AC power supply, in an embodiment, thecontrol unit 124-8 sets its mode of operation to AC, as discussed above.In this mode, control unit 124-8 controls the semiconductor switch Q1 ina manner to resemble a switching operation of a phase controlled switchsuch as a triac. Specifically, the switch Q1 is turned ON by the controlunit 124-8 correspondingly to a point of the AC half cycle where a triacwould normally be fired. The control unit 124-8 continued to keep theswitch Q1 ON until a zero-crossing has been reached, which indicates theend of the AC half cycle. At that point, control unit 124-8 turns switchQ1 OFF correspondingly to the point of current zero crossing. In thismanner the control unit 124-8 controls the speed of the motor by turningswitch Q1 ON within each half cycle to control the conduction angle ofeach AC half cycle according to the desired speed of the motor.

When power is supplied via DC power lines DC+/DC−, current flows throughD1-Q1-D2 into the motor 124-2. As mentioned above, control unit 124-8controls the speed of the motor by controlling a PWM duty cycle ofswitch Q1. When power is supplied via AC power lines ACH/ACL, currentflows through D1-Q1-D2 during every positive half-cycle, and throughD3-Q1-D4 through every negative half-cycle. Thus, the diode bridge D1-D4acts to rectify the AC power passing through the switch Q1, but it doesnot rectify the AC power passing through the motor terminals M+/M−. Asmentioned above, control unit 124-8 controls the speed of the motor bycontrolling a conduction band of each half cycle via switch Q1.

It is noted that in an embodiment, control unit 124-8 may perform PWMcontrol on switch Q1 in both the AC and DC modes of operation.Specifically, instead of controlling a conduction band of the AC linewithin each half-cycle, control unit 124-8 may select a PWM duty cycleand using the PWM technique discussed above to control the speed of themotor.

Depending on the motor 124-2 size and property, motor 124-2 may have aninductive current that is slightly delayed with respect to the AC linecurrent. In the AC mode of operation, this current is allowed to decaydown to zero at the end of each AC half cycle, i.e., after every voltagezero crossing. However, in the DC mode of operation, it is desirable toprovide a current path for the inductive current of the motor 124-2.Thus, according to an embodiment, a freewheeling switch Q2 and afreewheeling diode D5 are further provided parallel to the motor 124-2to provide a path for the inductive current flowing through the motor124-2 when Q1 has been turned OFF. In an embodiment, in the AC mode ofoperation, control unit 124-8 is configured to keep Q2 OFF at all times.However, in the DC mode of operation, control unit 124-8 is configuredto keep freewheeling switch Q2 ON.

In a further embodiment, control unit 124-8 is configured to turn Q2 ONwhen switch Q1 is turned OFF, and vice versa. In other words, when Q1 isbeing pulse-width modulated, the ON and OFF periods of switch Q1 willsynchronously coincide with the OFF and ON periods of switch Q2. Thisensures that the freewheeling current path of Q2/D5 does not short themotor 124-8 during any Q1 ON cycle.

With such arrangement, the speed of motor 124-2 can be controlledregardless of whether power tool 124 is connected to an AC or a DC powersupply.

2. Variable-Speed Universal Motor Tools with Power Supplies HavingComparable Voltage Ratings

In FIGS. 7A, 7B, and 7F described above, power tools 124 are designed tooperate at a high-rated voltage range of, for example, 100V to 120V(which corresponds to the AC power voltage range of 100V to 120 VAC), ormore broadly, 90V to 132V (which corresponds to ±10% of the AC powervoltage range of 100 to 120 VAC), and at high power (e.g., 1500 to 2500Watts). The motor 124-2 also has an operating voltage or operatingvoltage range that may be equivalent to, fall within, or correspond tothe operating voltage or the operating voltage range of the tool 124.

In an embodiment, the power supply interface 124-5 is arranged toprovide an AC voltage having a nominal voltage that is significantlydifferent from a nominal voltage provided from the DC power supply. Forexample, the AC power line of the power supply interface 124-5 mayprovide a nominal voltage in the range of 100 to 120V, and the DC powerline may provide a nominal voltage in the range of 60V-100V (e.g., 72VDC or 90 VDC). In another example, the AC power line may provide anominal voltage in the range of 220 to 240V (e.g., 230V in many Europeancountries or 220V in many African countries), and the DC power line mayprovide a nominal voltage in the range of 100-120V (e.g., 108 VDC).

3. Variable-Speed Universal Motor Tools with Power Supplies HavingDisparate Voltage Ratings

According to an alternative embodiment of the invention, voltageprovided by the AC power supply has a nominal voltage that issignificantly different from a nominal voltage provided from the DCpower supply. For example, the AC power line of the power supplyinterface 124-5 may provide a nominal voltage in the range of 100 to120V, and the DC power line may provide a nominal voltage in the rangeof 60V-100V (e.g., 72 VDC or 90 VDC). In another example, the AC powerline may provide a nominal voltage in the range of 220 to 240V (e.g.,230V in many European countries or 220V in many African countries), andthe DC power line may provide a nominal voltage in the range of 100-120V(e.g., 108 VDC).

Operating the power tool motor 124-2 at significantly different voltagelevels may yield significant differences in power tool performance, inparticular the rotational speed of the motor, which may be noticeableand in some cases unsatisfactory to the users. Also supplying voltagelevels outside the operating voltage range of the motor 124-2 may damagethe motor and the associated switching components. Thus, in anembodiment of the invention herein described, the motor control circuit124-4 is configured to optimize a supply of power to the motor (and thusmotor performance) 124-2 depending on the nominal voltage of the AC orDC power lines such that motor 124-2 yields substantially uniform speedand power performance in a manner satisfactory to the end user,regardless of the nominal voltage provided on the AC or DC power lines.

In this embodiment, motor 124-2 may be designed and configured tooperate at a voltage range that encompasses the nominal voltage of theDC power line. In an exemplary embodiment, motor 124-2 may be designedto operate at a voltage range of for example 60V to 90V (or more broadly±10% at 54V to 99V) encompassing the nominal voltage of the DC powerline of the power supply interface 124-5 (e.g., 72 VDC or 90 VDC), butlower than the nominal voltage of the AC power line (e.g., 220V-240V).In another exemplary embodiment, motor 124-2 may be designed to operateat a voltage range of 100V to 120V (or more broadly ±10% at 90V to132V), encompassing the nominal voltage of the DC power line of thepower supply interface 124-5 (e.g., 108 VDC), but lower than the nominalvoltage range of 220-240V of the AC power line.

In an embodiment, in order for motor 124-2 to operate to operate withthe higher nominal voltage of the AC power line, control unit 124-8 maybe configured to set a fixed maximum conduction band for thephase-controlled AC switch 124-16 corresponding to the operating voltageof the tool 124. Specifically, the control unit 124-8 may be configuredto set a fixed firing angle corresponding to the maximum speed of thetool (e.g., at 100% trigger displacement) resulting in a conduction bandof less than 180 degrees within each AC half-cycle at maximum no-loadspeed. This allows the control unit 124-8 to optimize the supply ofpower to the motor by effectively reducing the total voltage provided tothe motor 124-2 from the AC power supply.

For example, for a motor 124-2 having an operating voltage range of 60to 100V but receiving AC power having a nominal voltage of 100-120V, theconduction band of the AC switch 124-16 may be set to a maximum ofapproximately 120 degrees. In other words, the firing angle of the ACswitch 124-16 may be varied from 60 degrees (corresponding to 120degrees conduction angle) at full desired speed to 180 degrees(corresponding to 0 degree conduction angle) at no-speed. By setting themaximum firing angle to approximately 60 degrees, the AC voltagesupplied to the motor at full desired speed will be approximately in therange of 70-90V, which corresponds to the operating voltage of the tool124.

In this manner, motor control circuit 124-4 optimizes a supply of powerto the motor 124-2 depending on the nominal voltage of the AC or DCpower lines such that motor 124-2 yields substantially uniform speed andpower performance in a manner satisfactory to the end user, regardlessof the nominal voltage provided on the AC or DC power lines.

C. Constant-Speed AC/DC Power Tools with Brushed PMDC Motors

Turning now to FIGS. 8A and 8B, the third subset of AC/DC power toolswith brushed motors 122 includes constant-speed AC/DC power tools 125with permanent magnet DC (PMDC) brushed motors (herein referred to asconstant-speed PMDC tools 125), which tend to be more efficient thanuniversal motors. These include corded/cordless (AC/DC) power tools thatoperate at constant speed at no load (or constant load) and include PMDCbrushed motors 125-2 configured to operate at a high rated voltage(e.g., 100V to 120V) and high power (e.g., 1500 to 2500 Watts). A PMDCbrushed motor generally includes a wound rotor coupled to a commutator,and a stator having permanent magnets affixed therein. A PMDC motor, asthe name implies, works with DC power only. This is because thepermanent magnets on the stator do not change polarity, and as the ACpower changes from a positive half-cycle to a negative half-cycle, thepolarity change in the brushes brings the motor to a stand-still. Forthis reason, in an embodiment, as shown in FIGS. 8A and 8B, power fromthe AC power supply is passed through a rectifier circuit 125-20 toconvert or remove the negative half-cycles of the AC power. In anembodiment, rectifier circuit 125-20 may be a full-wave rectifierarranged to rectify the AC voltage waveform by converting the negativehalf-cycles of the AC power to positive half-cycles. Alternatively, inan embodiment, rectifier circuit 125-20 may be a half-wave rectifiercircuit to eliminate the half-cycles of the AC power. In an embodiment,the rectifier circuit 125-20 may be additionally provided with a linkcapacitor or a smoothing capacitor (not shown). In an embodiment,constant-speed PMDC motor tools 125 may include high powered tools forhigh power applications such as concrete hammers, miter saws, tablesaws, vacuums, blowers, and lawn mowers, etc.

Many aspects of the constant-speed PMDC motor tool 125 are similar tothose of the constant-speed universal motor tool 123 previouslydiscussed with reference to FIGS. 6A-6E. In an embodiment, aconstant-speed PMDC motor tool 125 includes a motor control circuit125-4 that operates the PMDC motor 125-2 at a constant speed under noload. The power tool 125 further includes power supply interface 125-5arranged to receive power from one or more of the aforementioned DCpower supplies and/or AC power supplies. The power supply interface125-5 is electrically coupled to the motor control circuit 125-4 by DCpower lines DC+ and DC− (for delivering power from a DC power supply)and by AC power lines ACH and ACL (for delivering power from an AC powersupply).

In an embodiment, motor control circuit 125-4 includes a power unit125-6. Power unit 125-6 may include an electro-mechanical ON/OFF switch125-12 provided in series with the motor 125-2 and coupled to an ON/OFFtrigger or actuator (not shown). Additionally and/or alternatively,power unit 125 may include a power switch 125-13 coupled to the DC powerlines DC+/DC− and to a control unit 125-8. In an embodiment, controlunit 125-8 may be provided to monitor the power tool 125 and/or batteryconditions. In an embodiment, control unit 125-8 may be coupled to tool125 elements such as a thermistor inside a tool. In an embodiment,control unit 125-8 may also be coupled to the battery pack(s) via acommunication signal line COMM provided from power supply interface125-5. The COMM signal line may provide a control or informationalsignal relating to the operation or condition of the battery pack(s) tothe control unit 125-8. In an embodiment, control unit 125-8 may beconfigured to cut off power from the DC+ output line of power supplyinterface 125-5 using the power switch 125-13 if tool fault conditions(e.g., tool over-temperature, tool over-current, etc.) or battery faultconditions (e.g., battery over-temperature, battery over-current,battery over-voltage, battery under-voltage, etc.) are detected. In anembodiment, power switch 125-13 may include a FET or other controllableswitch that is controlled by control unit 125-8. It is noted that powerswitch 125-13 in an alternative embodiment may be provided between bothAC power lines ACH/ACL and DC power lines DC+/DC− on one side and themotor 125-2 on the other side to allow the control unit 125-8 to cut offpower from either the AC power supply or the DC power supply in theevent of a tool fault condition. Also in another embodiment,constant-speed PMDC motor tool 125 may be provided without an ON/OFFswitch 125-12, and the control unit 125-8 may be configured to beginactivating the power switch 125-13 when the ON/OFF trigger or actuatoris actuated by a user. In other words, power switch 125-13 may be usedfor ON/OFF and fault condition control. It is noted that power switch125-13 is not used to control a variable-speed control (e.g., PWMcontrol) of the motor 125-2 in this embodiment.

Referring to FIG. 8A, constant-speed PMDC motor tool 125 is depictedaccording to one embodiment, where the DC+ power line and V+ output ofthe rectifier circuit 125-20 (which carries the rectified ACH powerline) are coupled together at common positive node 125-11 a, and the DC−power line and Gnd output (corresponding to ACL power line) from therectifier circuit 125-20 are coupled together at a common negative node125-11 b. In this embodiment, ON/OFF switch 125-12 is arranged betweenthe positive common node 125-11 a and the motor 125-2. To ensure thatonly one of the AC or DC power supplies are utilized at any given time,in an embodiment, a mechanical lockout may be utilized. In an exemplaryembodiment, the mechanical lockout may physically block access to theone of the AC or DC power supplies at any given time.

In FIG. 8B, constant-speed PMDC motor tool 125 is depicted according toan alternative embodiment, where the DC power lines DC+/DC− and the ACpower lines ACH/ACL are isolated via a power supply switching unit125-15 to ensure that power cannot be supplied from both the AC powersupply and the DC power supply at the same time (even if the powersupply interface 125-5 is coupled to both AC and DC power supplies). Thepower supply switching unit 125-15 may be configured similarly to any ofthe configurations of power supply switching unit 123-15 in FIGS. 6B-6D.It is noted that power supply switching unit 125-15 may be arrangedbetween the AC power lines ACH/ACL and the rectifier circuit 125-20 inan alternative embodiment. In yet another embodiment, power supplyswitching unit 125-15 may be arranged between the power switch 125-13and the ON/OFF switch 125-12.

It should be understood that while tool 125 in FIGS. 8A and 8B isprovided with a control unit 125-8 and power switch 125-13 to cut offsupply of power in an event of a tool or battery fault condition, tool125 may be provided without a control unit 125-8 and a power switch125-13. For example, the battery pack(s) may be provided with its owncontroller to monitor its fault conditions and manage its operations.

1. Constant Speed PMDC Tools with Power Supplies Having ComparableVoltage Ratings

In FIGS. 8A and 8B described above, power tools 125 are designed tooperate at a high-rated voltage range of, for example, 100V to 120V(which corresponds to the AC power voltage range of 100V to 120 VAC),more broadly 90V to 132V (which corresponds to ±10% of the AC powervoltage range of 100 to 120 VAC), and at high power (e.g., 1500 to 2500Watts). The motor 125-2 also has an operating voltage or operatingvoltage range that may be equivalent to, fall within, or correspond tothe operating voltage or the operating voltage range of the tool 125.

In an embodiment, the power supply interface 125-5 is arranged toprovide AC power line having a nominal voltage in the range of 100 to120V (e.g., 120 VAC at 50-60 Hz in the US, or 100 VAC in Japan) from anAC power supply, or a DC power line having a nominal voltage in therange of 100 to 120V (e.g., 108 VDC) from a DC power supply. In otherwords, the DC nominal voltage and the AC nominal voltage providedthrough the power supply interface 125-5 both correspond to (e.g.,match, overlap with, or fall within) the operating voltage range of thepower tool 125 (i.e., high-rated voltage 100V to 120V, or more broadlyapproximately 90V to 132V). It is noted that a nominal voltage of 120VAC corresponds to an average voltage of approximately 108V whenmeasured over the positive half cycles of the AC sinusoidal waveform,which provides an equivalent speed performance as 108 VDC power.

2. Constant Speed PMDC Tools with Power Supplies Having DisparateVoltage Ratings

According to another embodiment of the invention, voltage provided bythe AC power supply has a nominal voltage that is significantlydifferent from a nominal voltage provided from the DC power supply. Forexample, the AC power line of the power supply interface 125-5 mayprovide a nominal voltage in the range of 100 to 120V, and the DC powerline may provide a nominal voltage in the range of 60V-100V (e.g., 72VDC or 90 VDC). In another example, the AC power line may provide anominal voltage in the range of 220 to 240V, and the DC power line mayprovide a nominal voltage in the range of 100-120V (e.g., 108 VDC).

Operating the power tool motor 125-2 at significantly different voltagelevels may yield significant differences in power tool performance, inparticular the rotational speed of the motor, which may be noticeableand in some cases unsatisfactory to the users. Also supplying voltagelevels outside the operating voltage range of the motor 125-2 may damagethe motor and the associated switching components. Thus, in anembodiment of the invention herein described, the motor control circuit125-4 is configured to optimize a supply of power to the motor (and thusmotor performance) 125-2 depending on the nominal voltage of the AC orDC power lines such that motor 125-2 yields substantially uniform speedand power performance in a manner satisfactory to the end user,regardless of the nominal voltage provided on the AC or DC power lines.

In this embodiment, power tool motor 125-2 may be designed andconfigured to operate at a voltage range that encompasses the nominalvoltage of the DC power line. In an exemplary embodiment, motor 125-2may be designed to operate at a voltage range of for example 60V to 90V(or more broadly ±10% at 54V to 99V) encompassing the nominal voltage ofthe DC power line of the power supply interface 125-5 (e.g., 72 VDC or90 VDC), but lower than the nominal voltage of the AC power line (e.g.,220V-240V). In another exemplary embodiment, motor 125-2 may be designedto operate at a voltage range of 100V to 120V (or more broadly ±10% at90V to 132V), encompassing the nominal voltage of the DC power line ofthe power supply interface 125-5 (e.g., 108 VDC), but lower than thenominal voltage range of 220-240V of the AC power line.

In an embodiment, in order for motor 125-2 to operate with the highernominal voltage of the AC power line, motor control circuit 125-4 may bedesigned to optimize supply of power to the motor 125-2 according tovarious implementations discussed herein.

In one implementation, rectifier circuit 125-20 may be provided as ahalf-wave diode bridge rectifier. As persons skilled in the art shallrecognize, a half-wave rectified waveform will have about approximatelyhalf the average nominal voltage of the input AC waveform. Thus, in ascenario where the nominal voltage of the AC power line is in the rangeof 220-240V and the motor 125-2 is designed to operate at a voltagerange of 100V to 120V, the rectifier circuit 125-20 may be configured asa half-wave rectifier to provide an average nominal AC voltage of 110Vto 120V to the motor 125-2, which is within the operating voltage rangeof the power tool 125.

In another implementation, as shown in FIG. 8C, the V+ output of therectifier circuit 125-20 may be provided as an input to power switch125-13, and control unit 125-8 may be configured to pulse width modulate(PWM) the V+ signal at a fixed duty cycle corresponding to the operatingvoltage of the tool 125. For example, for a tool 125 having an operatingvoltage range of 60 to 100V but receiving AC power having a nominalvoltage of 100-120V, when control unit 125-8 senses AC current on the ACpower line of power supply interface 125-5, it controls a PWM switchingoperation of power switch 125-13 at fixed duty cycle in the range of 60%to 80% (e.g., 70%). This results in a voltage level of approximately70-90V being supplied to the motor 125-2 when operating from an AC powersupply, which corresponds to the operating voltage of the tool 125.

In yet another implementation, as shown in FIG. 8D, tool 125 may befurther provided with a phase-controlled AC switch 125-16. In anembodiment, AC switch 125-16 is arranged in series with the V+ output ofthe rectifier circuit 125-20. In an embodiment, AC switch 125-16 mayinclude a triac or an SRC switch controlled by the control unit 125-8.In an embodiment, the control unit 125-8 may be configured to set afixed conduction band (or firing angle) of the AC switch 125-16corresponding to the operating voltage of the tool 125. For example, fora motor 125-2 having an operating voltage range of 60 to 100V butreceiving AC power having a nominal voltage of 100-120V, the conductionband of the AC switch 125-16 may be fixedly set to approximately 120degrees. In other words, the firing angle of the AC switch 125-16 may beset to 60 degrees. By setting the firing angle to approximately 60degrees, the AC voltage supplied to the motor 125-2 will beapproximately in the range of 70-90V, which corresponds to the operatingvoltage of the motor 125-2. In another example, for a motor 125-2 havingan operating voltage range of 100 to 120V but receiving AC power havinga nominal voltage of 220-240V, the conduction band of the AC switch125-16 may be fixedly set to approximately 90 degrees. In other words,the firing angle of the AC switch 125-16 may be set to 90 degrees. Bysetting the firing angle to 90 degrees, the AC voltage supplied to themotor 125-2 will be approximately in the range of 100-120V, whichcorresponds to the operating voltage of the motor 125-2. In this manner,control unit 125-8 optimizes the supply of power to the motor 125-2.

In this manner, motor control circuit 125-4 optimizes a supply of powerto the motor 125-2 depending on the nominal voltage of the AC or DCpower lines such that motor 125-2 yields substantially uniform speed andpower performance in a manner satisfactory to the end user, regardlessof the nominal voltage provided on the AC or DC power lines.

D. Variable-Speed AC/DC Power Tools with Brushed DC Motors

Turning now to FIG. 9A-9B, the fourth subset of AC/DC power tools withbrushed motors 122 includes variable-speed AC/DC power tools 126 withPMDC motors (herein also referred to as variable-speed PMDC motor tools126). These include corded/cordless (AC/DC) power tools that operate atvariable speed at no load and include brushed permanent magnet DC (PMDC)motors 126-2 configured to operate at a high rated voltage (e.g., 100 to120V) and high power (e.g., 1500 to 2500 Watts). As discussed above, aPMDC brushed motor generally includes a wound rotor coupled to acommutator, and a stator having permanent magnets affixed therein. APMDC motor, as the name implies, works with DC power only. This isbecause the permanent magnets on the stator do not change polarity, andas the AC power changes from a positive half-cycle to a negativehalf-cycle, the polarity change in the brushes brings the motor to astand-still. For this reason, in an embodiment, as shown in FIGS. 9A and9B, power from the AC power supply is passed through a rectifier circuit126-20 to convert or remove the negative half-cycles of the AC power. Inan embodiment, rectifier circuit 126-20 may be a full-wave rectifier toconvert the negative half-cycles of the AC power to positivehalf-cycles. Alternatively, in an embodiment, rectifier circuit 126-20may be a half-wave rectifier circuit to eliminate the half-cycles of theAC power. In an embodiment, variable-speed PMDC motor tools 126 mayinclude high-power tools having variable speed control, such as concretedrills, hammers, grinders, saws, etc.

Many aspects of the variable-speed PMDC motor tool 126 are similar tothose of variable-speed universal motor tool 124 previously discussedwith reference to FIGS. 7A-7E. In an embodiment, variable-speed PMDCmotor tool 126 is provided with a variable-speed actuator (not shown,e.g., a trigger switch, a touch-sense switch, a capacitive switch, agyroscope, or other variable-speed input mechanism) engageable by auser. In an embodiment, the variable-speed actuator is coupled to orincludes a potentiometer or other circuitry for generating avariable-speed signal (e.g., variable voltage signal, variable currentsignal, etc.) indicative of the desired speed of the motor 126-2. In anembodiment, variable-speed PMDC motor tool 126 may be additionallyprovided with an ON/OFF trigger or actuator (not shown) enabling theuser to start the motor 126-2. Alternatively, the ON/OFF triggerfunctionally may be incorporated into the variable-speed actuator (i.e.,no separate ON/OFF actuator) such that an initial actuation of thevariable-speed trigger by the user acts to start the motor 126-2.

In an embodiment, a variable-speed PMDC motor tool 126 includes a motorcontrol circuit 126-4 that operates the PMDC motor 126-2 at variablespeed under no load or constant load. The power tool 126 furtherincludes power supply interface 126-5 arranged to receive power from oneor more of the aforementioned DC power supplies and/or AC powersupplies. The power supply interface 126-5 is electrically coupled tothe motor control circuit 126-4 by DC power lines DC+ and DC− (fordelivering power from a DC power supply) and by AC power lines ACH andACL (for delivering power from an AC power supply). The AC power linesACH and ACL are inputted into the rectifier circuit 126-20.

Since the AC line is passed through the rectifier circuit 126-20, it nolonger includes a negative component and thus, in an embodiment, doesnot work with a phase controlled switch for variable-speed control.Thus, in an embodiment, instead of separate DC and AC switch circuits asshown in FIGS. 7A and 7B, motor control circuit 126-4 is provided with aPWM switching circuit 126-14. PWM switching circuit may include acombination of one or more power semiconductor devices (e.g., diode,FET, BJT, IGBT, etc.) arranged as a chopper circuit, a half-bridge, oran H-bridge, e.g., as shown in FIGS. 7C-7E.

In an embodiment, motor control circuit 126-4 further includes a controlunit 126-8. Control unit 126-8 may be arranged to control a switchingoperation of the PWM switching circuit 126-14. In an embodiment, controlunit 126-8 may include a micro-controller or similar programmable moduleconfigured to control gates of power switches. In an embodiment, thecontrol unit 126-8 is configured to control a PWM duty cycle of one ormore semiconductor switches in the PWM switching circuit 126-14 in orderto control the speed of the motor 126-2. In addition, control unit 126-8may be configured to monitor and manage the operation of the power toolor battery packs coupled to the power supply interface 126-5 andinterrupt power to the motor 126-2 in the event of a tool or batteryfault condition (such as, battery over-temperature, toolover-temperature, battery over-current, tool over-current, batteryover-voltage, battery under-voltage, etc.). In an embodiment, controlunit 126-8 may be coupled to the battery pack(s) via a communicationsignal line COMM provided from power supply interface 126-5. The COMMsignal line may provide a control or informational signal relating tothe operation or condition of the battery pack(s) to the control unit126-6. In an embodiment, control unit 126-6 may be configured to cut offpower from the DC output line of power supply interface 126-5 if theCOMM line indicates a battery failure or fault condition.

Similar to variable-speed universal motor tool 124 previously discussedwith reference to FIGS. 7A-7E, variable-speed PMDC motor tool 126 may befurther provided with an electro-mechanical ON/OFF switch 126-12 coupledto the ON/OFF trigger or actuator discussed above. The ON/OFF switch126-12 simply connects or disconnects supply of power from the powersupply to the motor 126-2. Alternatively, tool 126 may be providedwithout an ON/OFF switch 126-12. In that case, control unit 126-8 may beconfigured to deactivate PWM switching circuit 126-14 until it detects auser actuation of the ON/OFF trigger or actuator (or initial actuator ofthe variable-speed actuator if ON/OFF trigger functionally is beincorporated into the variable-speed actuator). The control unit 126-8may then begin operating the motor 126-2 by activating one or more ofthe switches in PWM switching circuit 126-14.

Referring to FIG. 9A, the tool 126 is depicted according to oneembodiment, where the ACH and DC+ power lines are coupled together atcommon positive node 126-11 a, and the ACL and DC− power lines arecoupled together at a common negative node 126-11 b. In this embodiment,ON/OFF switch 126-12 and PWM switching circuit 126-14 are arrangedbetween the positive common node 126-11 a and the motor 126-2. To ensurethat only one of the AC or DC power supplies are utilized at any giventime and to minimize leakage, in an embodiment, a mechanical lockout(embodiments of which are discussed in more detail below) may beutilized. In an exemplary embodiment, the mechanical lockout mayphysically block access to the AC or DC power supplies at any giventime.

In FIG. 9B, variable-speed PMDC motor tool 126 is depicted according toan alternative embodiment, where the DC power lines DC+/DC− and the ACpower lines ACH/ACL are isolated from each other via a power supplyswitching unit 126-15 to ensure that power cannot be supplied from boththe AC power supply and battery pack(s) at the same time (even if thepower supply interface is coupled to both AC and DC power supplies). Thepower supply switching unit 126-15 may be configured similarly to any ofthe configurations of power supply switching unit 123-15 in FIGS. 6B-6D,i.e., relays, single-pole double-throw switches, double-poledouble-throw switches, or a combination thereof. It must be understoodthat while the power supply switching unit 126-15 in FIG. 9B is depictedbetween the rectifier circuit 126-20 and the PWM switching circuit126-14, the power supply switching unit 126-15 may alternatively beprovided directly on the AC and DC line outputs of the power supplyinterface 126-5.

1. Variable-Speed Brushed DC Tools with Power Supplies Having ComparableVoltage Ratings

In FIGS. 9A and 9B described above, power tools 126 are designed tooperate at a high-rated voltage range of, for example, 100V to 120V(which corresponds to the AC power voltage range of 100V to 120 VAC),more broadly 90V to 132V (which corresponds to ±10% of the AC powervoltage range of 100 to 120 VAC), and at high power (e.g., 1500 to 2500Watts). Specifically, the motor 126-2 and power unit 126-6 components ofpower tools 126 are designed and optimized to handle high-rated voltageof 100 to 120V, preferably 90V to 132V. The motor 126-2 also has anoperating voltage or operating voltage range that may be equivalent to,fall within, or correspond to the operating voltage or the operatingvoltage range of the tool 126.

In an embodiment, the power supply interface 126-5 is arranged toprovide AC power line having a nominal voltage in the range of 100 to120V (e.g., 120 VAC at 50-60 Hz in the US, or 100 VAC in Japan) from anAC power supply, or a DC power line having a nominal voltage in therange of 100 to 120V (e.g., 108 VDC) from a DC power supply. In otherwords, the DC nominal voltage and the AC nominal voltage providedthrough the power supply interface 126-5 both correspond to (e.g.,match, overlap with, or fall within) the operating voltage range of thepower tool 125 (i.e., high-rated voltage 100V to 120V, or more broadlyapproximately 90V to 132V). It is noted that a nominal voltage of 120VAC corresponds to an average voltage of approximately 108V whenmeasured over the positive half cycles of the AC sinusoidal waveform,which provides an equivalent speed performance as 108 VDC power.

2. Variable-Speed Brushed DC Tools with Power Supplies Having DisparateVoltage Ratings

According to another embodiment of the invention, voltage provided bythe AC power supply has a nominal voltage that is significantlydifferent from a nominal voltage provided from the DC power supply. Forexample, the AC power line of the power supply interface 126-5 mayprovide a nominal voltage in the range of 100 to 120V, and the DC powerline may provide a nominal voltage in the range of 60V-100V (e.g., 72VDC or 90 VDC). In another example, the AC power line may provide anominal voltage in the range of 220 to 240V, and the DC power line mayprovide a nominal voltage in the range of 100-120V (e.g., 108 VDC).

Operating the power tool motor 126-2 at significantly different voltagelevels may yield significant differences in power tool performance, inparticular the rotational speed of the motor, which may be noticeableand in some cases unsatisfactory to the users. Also supplying voltagelevels outside the operating voltage range of the motor 126-2 may damagethe motor and the associated switching components. Thus, in anembodiment of the invention herein described, the motor control circuit126-4 is configured to optimize a supply of power to the motor (and thusmotor performance) 126-2 depending on the nominal voltage of the AC orDC power lines such that motor 126-2 yields substantially uniform speedand power performance in a manner satisfactory to the end user,regardless of the nominal voltage provided on the AC or DC power lines.

In this embodiment, motor 126-2 may be designed and configured tooperate at a voltage range that encompasses the nominal voltage of theDC power line. In an exemplary embodiment, motor 126-2 may be designedto operate at a voltage range of for example 60V to 90V (or more broadly±10% at 54V to 99V) encompassing the nominal voltage of the DC powerline of the power supply interface 126-5 (e.g., 72 VDC or 90 VDC), butlower than the nominal voltage of the AC power line (e.g., 220V-240V).In another exemplary embodiment, motor 126-2 may be designed to operateat a voltage range of 100V to 120V (or more broadly ±10% at 90V to132V), encompassing the nominal voltage of the DC power line of thepower supply interface 126-5 (e.g., 108 VDC), but lower than the nominalvoltage range of 220-240V of the AC power line.

In order for motor 126-2 to operate with the higher nominal voltage ofthe AC power line, the motor control circuit 126-4 may be design tooptimize supply of power to the motor 126-2 according to variousimplementations discussed herein.

In one implementation, rectifier circuit 126-20 may be provided as ahalf-wave diode bridge rectifier. As persons skilled in the art shallrecognize, a half-wave rectified waveform will have about approximatelyhalf the average nominal voltage of the input AC waveform. Thus, in ascenario where the nominal voltage of the AC power line is in the rangeof 220-240V and the motor 126-2 is designed to operate at a voltagerange of 100V to 120V, the rectifier circuit 126-20 configured as ahalf-wave rectifier will provide an average nominal AC voltage of110-120V to the motor 126-2, which is within the operating voltage rangeof the motor 126-2.

In another implementation, control unit 126-8 may be configured tocontrol the PWM switching circuit 126-14 differently based on the inputvoltage being provided. Specifically, control unit 126-8 may beconfigured to perform PWM on the PWM switching circuit 126-14 switchesat a normal duty cycle range of 0 to 100% in DC mode (i.e., when poweris being supplied via DC+/DC− lines), and perform PWM on the switches ata duty cycle range from 0 to a maximum threshold value corresponding tothe operating voltage of the motor 126-2 in AC mode (i.e., when power isbeing supplied via ACH/ACL lines).

For example, for a motor 126-2 having an operating voltage range of 60to 100V but receiving AC power having a nominal voltage of 100-120V,when control unit 126-8 senses AC current on the AC power line of powersupply interface 126-5, it controls a PWM switching operation of PWMswitching circuit 126-14 at duty cycle in the range of from 0 up to amaximum threshold value, e.g., 70%. In this embodiment, running atvariable speed, the duty cycle will be adjusted according to the maximumthreshold duty cycle. Thus, for example, when running at half-speed, thePWM switching circuit 126-14 may be run at 35% duty cycle. This resultsin a voltage level of approximately 70-90V being supplied to the motor126-2 when operating from an AC power supply, which corresponds to theoperating voltage of the motor 126-2.

In this manner, motor control circuit 126-4 optimizes a supply of powerto the motor 126-2 depending on the nominal voltage of the AC or DCpower lines such that motor 126-2 yields substantially uniform speed andpower performance in a manner satisfactory to the end user, regardlessof the nominal voltage provided on the AC or DC power lines.

E. AC/DC Power Tools with Brushless Motors

Referring now to FIGS. 10A-10C, the set of AC/DC power tools 128 withbrushless motors (herein referred to as brushless tools 128) isdescribed herein. In an embodiment, these include constant speed orvariable speed AC/DC power tools with brushless DC (BLDC) motors 202that are electronically commutated (i.e., are not commutated viabrushes) and are configured to operate at a high rated voltage (e.g.,100-120V, preferably 90V to 132V) and high power (e.g., 1500 to 2500Watts). A brushless motor described herein may be a three-phasepermanent magnet synchronous motor including a rotor having permanentmagnets and a wound stator that is commutated electronically asdescribed below. The stator windings are designated herein as U, V, andW windings corresponding to the three phases of the motor 202. The rotoris rotationally moveable with respect to the stator when the phases ofthe motor 202 (i.e., the stator windings) are appropriately energized.It should be understood, however, that other types of brushless motors,such as switched reluctance motors and induction motors, are within thescope of this disclosure. It should also be understood that the BLDCmotor 202 may include fewer than or more than three phases. For detailsof a BLDC motor construction and control, reference is made to U.S. Pat.Nos. 6,538,403, 6,975,050, U.S. Patent Publication No. 2013/0270934, allof which are assigned to Black & Decker Inc. and each of which isincorporated herein by reference in its entirety.

In an embodiment, brushless tools 128 may include high powered tools forvariable speed applications such as concrete drills, hammers, grinders,and reciprocating saws, etc. Brushless tools 128 may also include highpowered tools for constant speed applications such as concrete hammers,miter saws, table saws, vacuums, blowers, and lawn mowers, etc.

In an embodiment, a brushless tool 128 can be operated at constant speedat no load (or constant load), or at variable speed at no load (orconstant load) based on an input from a variable-speed actuator (notshown, e.g., a trigger switch, a touch-sense switch, a capacitiveswitch, a gyroscope, or other variable-speed input mechanism engageableby a user) arranged to provide a variable analog signal (e.g., variablevoltage signal, variable current signal, etc.) indicative of the desiredspeed of the BLDC motor 202. In an embodiment, brushless tool 128 may beadditionally provided with an ON/OFF trigger or actuator (not shown)enabling the user to start the motor 202. Alternatively, the ON/OFFtrigger functionally may be incorporated into the variable-speedactuator (i.e., no separate ON/OFF actuator) such that an initialactuation of the variable-speed trigger by the user acts to start themotor 202.

In an embodiment, brushless tool 128 includes a power supply interface128-5 able to receive power from one or more of the aforementioned DCpower supplies and/or AC power supplies. The power supply interface128-5 is electrically coupled to the motor control circuit 204 by DCpower lines DC+ and DC− (for delivering power from a DC power supply)and by AC power lines ACH and ACL (for delivering power from an AC powersupply).

In an embodiment, brushless tool 128 further includes a motor controlcircuit 204 disposed to control supply of power from the power supplyinterface 128-5 to BLDC motor 202. In an embodiment, motor controlcircuit 204 includes a power unit 206 and a control unit 208, discussedbelow.

As the name implies, BLDC motors are designed to work with DC power.Thus, in an embodiment, as shown in FIGS. 10A and 10B, in an embodiment,power unit 206 is provided with a rectifier circuit 220. In anembodiment, power from the AC power lines ACH and ACL is passed throughthe rectifier circuit 220 to convert or remove the negative half-cyclesof the AC power. In an embodiment, rectifier circuit 220 may include afull-wave bridge diode rectifier 222 to convert the negative half-cyclesof the AC power to positive half-cycles. Alternatively, in anembodiment, rectifier circuit 220 may include a half-wave rectifier toeliminate the half-cycles of the AC power. In an embodiment, rectifiercircuit 220 may further include a link capacitor 224. As discussed laterin this disclosure, in an embodiment, link capacitor 224 has arelatively small value and does not smooth the full-wave rectified ACvoltage, as discussed below. In an embodiment, capacitor 224 is a bypasscapacitor that removes the high frequency noise from the bus voltage.

Power unit 206, in an embodiment, may further include a power switchcircuit 226 coupled between the power supply interface 128-5 and motorwindings to drive BLDC motor 202. In an embodiment, power switch circuit226 may be a three-phase bridge driver circuit including sixcontrollable semiconductor power devices (e.g. FETs, BJTs, IGBTs, etc.).

FIG. 10C depicts an exemplary power switch circuit 226 having athree-phase inverter bridge circuit, according to an embodiment. Asshown herein, the three-phase inverter bridge circuit includes threehigh-side FETs and three low-side FETs. The gates of the high-side FETsdriven via drive signals UH, VH, and WH, and the gates of the low-sideFETs are driven via drive signals UL, VL, and WL, as discussed below. Inan embodiment, the drains of the high-side FETs are coupled to thesources of the low-side FETs to output power signals PU, PV, and PW fordriving the BLDC motor 202.

Referring back to FIGS. 10A and 10B, control unit 208 includes acontroller 230, a gate driver 232, a power supply regulator 234, and apower switch 236. In an embodiment, controller 230 is a programmabledevice arranged to control a switching operation of the power devices inpower switching circuit 226. In an embodiment, controller 230 receivesrotor rotational position signals from a set of position sensors 238provided in close proximity to the motor 202 rotor. In an embodiment,position sensors 238 may be Hall sensors. It should be noted, however,that other types of positional sensors may be alternatively utilized. Itshould also be noted that controller 230 may be configured to calculateor detect rotational positional information relating to the motor 202rotor without any positional sensors (in what is known in the art assensorless brushless motor control). Controller 230 also receives avariable-speed signal from variable-speed actuator (not shown) discussedabove. Based on the rotor rotational position signals from the positionsensors 238 and the variable-speed signal from the variable-speedactuator, controller 230 outputs drive signals UH, VH, WH, UL, VL, andWL through the gate driver 232, which provides a voltage level needed todrive the gates of the semiconductor switches within the power switchcircuit 226 in order to control a PWM switching operation of the powerswitch circuit 226.

In an embodiment, power supply regulator 234 may include one or morevoltage regulators to step down the power supply from power supplyinterface 128-5 to a voltage level compatible for operating thecontroller 230 and/or the gate driver 232. In an embodiment, powersupply regulator 234 may include a buck converter and/or a linearregulator to reduce the power voltage of power supply interface 128-5down to, for example, 15V for powering the gate driver 232, and down to,for example, 3.2V for powering the controller 230.

In an embodiment, power switch 236 may be provided between the powersupply regulator 234 and the gate driver 232. Power switch 236 may be anON/OFF switch coupled to the ON/OFF trigger or the variable-speedactuator to allow the user to begin operating the motor 202, asdiscussed above. Power switch 236 in this embodiment disables supply ofpower to the motor 202 by cutting power to the gate drivers 232. It isnoted, however, that power switch 236 may be provided at a differentlocation, for example, within the power unit 206 between the rectifiercircuit 220 and the power switch circuit 226. It is further noted thatin an embodiment, power tool 128 may be provided without an ON/OFFswitch 236, and the controller 230 may be configured to activate thepower devices in power switch circuit 226 when the ON/OFF trigger (orvariable-speed actuator) is actuated by the user.

In an embodiment of the invention, in order to minimize leakage and toisolate the DC power lines DC+/DC− from the AC power lines ACH/ACL, apower supply switching unit 215 may be provided between the power supplyinterface 128-5 and the motor control circuit 204. The power supplyswitching unit 215 may be utilized to selectively couple the motor 202to only one of AC or DC power supplies. Switching unit 215 may beconfigured to include relays, single-pole double-throw switches,double-pole double-throw switches, or a combination thereof.

In the embodiment of FIG. 10A, power supply switching unit 215 includestwo double-pole single-throw switches 212, 214 coupled to the DC powerlines DC+/DC− and the AC power lines ACH/ACL. Switch 212 includes twoinput terminals coupled to DC+ and ACH terminals of the DC and AC lines,respectively. Similarly, switch 214 includes two input terminals coupledto DC− and ACL terminals of the DC and AC lines, respectively. Eachswitch 212, 214 includes a single output terminal, which is coupled tothe rectifier 222.

In an alternative embodiment shown in FIG. 10B, power supply switchingunit 215 two double-pole double-throw switches 216, 218 coupled to theDC power lines DC+/DC− and the AC power lines ACH/ACL. Switches switch216, 218 include two output terminals instead of one, which allow the DCpower line DC+/DC− to bypass rectifier 222 and be coupled directly tothe +/− terminals of the power switch circuit 226.

1. Brushless Tools with Power Supplies Having Comparable Voltage Ratings

In an embodiment, power tools 128 described above may be designed tooperate at a high-rated voltage range of, for example, 100V to 120V(which corresponds to the AC power voltage range of 100V to 120 VAC),more broadly 90V to 132V (which corresponds to ±10% of the AC powervoltage range of 100 to 120 VAC), and at high power (e.g., 1500 to 2500Watts). Specifically, the BLDC motor 202, as well as power unit 206 andcontrol unit 208 components, are designed and optimized to handlehigh-rated voltage of 100 to 120V, preferably 90V to 132V. The motor 202also has an operating voltage or operating voltage range that may beequivalent to, fall within, or correspond to the operating voltage orthe operating voltage range of the tool 128.

In an embodiment, the power supply interface 128-5 is arranged toprovide AC power line having a nominal voltage in the range of 100V to120V (e.g., 120 VAC at 50-60 Hz in the US, or 100 VAC in Japan) from anAC power supply, or a DC power line having a nominal voltage in therange of 100 to 120V (e.g., 108 VDC) from a DC power supply. In otherwords, the DC nominal voltage and the AC nominal voltage providedthrough the power supply interface 128-5 both correspond to (e.g.,match, overlap with, or fall within) each other and the operatingvoltage range of the power tool 128 (i.e., high-rated voltage 100V to120V, or more broadly approximately 90V to 132V). It is noted that anominal voltage of 120 VAC corresponds to an average voltage ofapproximately 108V when measured over the positive half cycles of the ACsinusoidal waveform, which provides an equivalent speed performance as108 VDC power. In an embodiment, as discussed in detail below, the linkcapacitor 224 is selected to have an optimal value that provides lessthan approximately 110V on the DC bus line from the 1210 VAC powersupply. In an embodiment, the link capacitor 224 may be less than orequal to 50 μF in one embodiment, less than or equal to 20 μF in oneembodiment, or less than or equal to 10 μF in one embodiment.

2. Brushless Tools with Power Supplies Having Disparate Voltage Ratings

According to an alternative embodiment of the invention, voltageprovided by the AC power supply has a nominal voltage that issignificantly different from a nominal voltage provided from the DCpower supply. For example, the AC power line of the power supplyinterface 128-5 may provide a nominal voltage in the range of 100 to120V, and the DC power line may provide a nominal voltage in the rangeof 60V-100V (e.g., 72 VDC or 90 VDC). In another example, the AC powerline may provide a nominal voltage in the range of 220 to 240V, and theDC power line may provide a nominal voltage in the range of 100-120V(e.g., 108 VDC).

Operating the BLDC motor 202 at significantly different voltage levelsmay yield significant differences in power tool performance, inparticular the rotational speed of the motor, which may be noticeableand in some cases unsatisfactory to the users. Also supplying voltagelevels outside the operating voltage range of the motor 202 may damagethe motor and the associated switching components. Thus, in anembodiment of the invention herein described, the motor control circuit204 is configured to optimize a supply of power to the motor (and thusmotor performance) 202 depending on the nominal voltage of the AC or DCpower lines such that motor 202 yields substantially uniform speed andpower performance in a manner satisfactory to the end user, regardlessof the nominal voltage provided on the AC or DC power lines.

Accordingly, in an embodiment, while the motor 202 may be designed andconfigured to operate at one or more operating voltage ranges thatcorrespond to both the nominal or rated voltages of the AC power supplyline and the DC power supply line, the motor 202 may be designed andconfigured to operate at a more limited operating voltage range that maycorrespond to (e.g., match, overlap and/or encompass) one or neither ofthe AC and DC power supply rated (or nominal) voltages.

For example, in one implementation, motor 202 may be designed andconfigured to operate at a voltage range that corresponds to the nominalvoltage of the DC power line. In an exemplary embodiment, motor 202 maybe designed to operate at a voltage range of, for example, 60V to 100V,that corresponds to the nominal voltage of the DC power supply (e.g., 72VDC or 90 VDC), but that is lower than the nominal voltage of the ACpower supply (100V-120V). In another exemplary embodiment, motor 202 maybe designed to operate at a voltage range of, for example, 100V to 120V,or more broadly 90 to 132V, that corresponds to the nominal voltage ofthe DC power supply (e.g., 108 VDC), but lower than the nominal voltagerange of 220-240V of the AC power supply. In this implementation,control unit 208 may be configured to reduce the effective motorperformance associated with the AC power line of the power supplyinterface 128-5 to correspond to the operating voltage range of themotor 202, as described below in detail.

In another implementation, motor 202 may be designed and configured tooperate at a voltage range that corresponds to the nominal voltage ofthe AC power supply. For example, motor 202 may be designed to operateat a voltage range of, for example 120V to 120V that corresponds to thenominal voltage of the AC power supply (e.g., 100 VAC to 120 VAC), buthigher than the nominal voltage of the DC power supply (e.g., 72 VDC or90 VDC). In this implementation, control unit 208 may be configured toboost the effective motor performance associated with the DC power lineto a level that corresponds to the operating voltage range of the motor202, as described below in detail.

In yet another implementation, motor 202 may be designed to operate at avoltage range of that does not correspond to either the AC or the DCnominal voltages. For example, motor 202 may be designed to operate at avoltage range of 150V to 170V, or more broadly 135V to 187V (which is±10% of the voltage range of 150 to 170 VAC), which may be higher thanthe nominal voltage of the DC power line of the power supply interface128-5 (e.g., 108 VDC), but lower than the nominal voltage range (e.g.,220-240V) of the AC power line. In this implementation, control unit 208may be configured to reduce the effective motor performance associatedwith the AC power line and boost the effective motor performanceassociated with the DC power line, as described below in detail.

In yet another implementation, motor 202 may be designed to operate at avoltage range that may or may not correspond to the DC nominal voltagesdepending on the type and rating of the battery pack(s) being used. Forexample, motor 202 may be designed to operate at a voltage range of, forexample 90V to 132V. This voltage range may correspond to the combinednominal voltage of some combination of battery packs previouslydiscussed (e.g. two medium-rated voltage packs for a combined nominalvoltage of 108 VDC), but higher than the nominal voltage of otherbattery pack(s) (e.g., a medium-rated voltage pack and a low-ratedvoltage pack used together for a combined nominal voltage of 72 VDC). Inthis implementation, control unit 208 may be configured to sense thevoltage received from the one or more battery pack(s) and optimize thesupply of power to the motor 202 accordingly. Alternatively, controlunit 208 may receive a signal from the coupled battery pack(s) or thebattery supply interface 128-5, indicating the type or rated voltage ofbattery pack(s) being used. In this implementation, control unit 208 maybe configured to reduce or boost the effective motor performanceassociated with the DC power line, as described below in detail,depending on the nominal voltage or the voltage rating of the batterypack(s) being used. Specifically, in an embodiment, control unit 208 maybe configured to reduce the effective motor performance associated withthe DC power line when the DC power supply has a higher nominal voltagethan the operating voltage range of the motor 202, and boost theeffective motor performance associated with the DC power line when theDC power supply has a lower nominal voltage than the operating voltagerange of the motor 202, as described below in detail.

Hereinafter, in the detailed discussion of techniques used to optimize(i.e., boost or lower) the effective performance of the motor 202relative to the nominal voltage levels of the AC and/or DC powersupplies and corresponding to the operating voltage range of the motor202, references are made to “lower rated voltage power supply” and“higher rated voltage power supply,” in an embodiment.

It is initially noted that while the embodiments below are describedwith reference to an AC/DC power tool operable to receive power supplieshaving disparate nominal (or rated) voltage levels, the principlesdiscloses here may apply to a cordless-only power tool and/or ancorded-only power tool as well. For example, in order for high ratedvoltage DC power tool 10A3 previously discussed (which may be optimizedto work at a high power and a high voltage rating) to work acceptablywith DC power supplies having a total voltage rating that is less thanthe voltage rating of the motor), the motor control circuit 14A may beconfigured to optimize the motor performance (i.e., speed and/or poweroutput performance of the motor) based on the rated voltage of the lowrated voltage DC battery packs 20A1. As discussed briefly above and indetail later in this disclosure, this may be done by optimizing (i.e.,booting or reducing) an effective motor performance from the powersupply to a level that corresponds to the operating voltage range (orvoltage rating) of the high rated voltage DC power tool 10A3.

3. Optimization of Physical Motor Characteristics Based on Power Supply

In the above-described embodiments, reference was made to a motor 202being designed to operate at a given operating voltage range inaccordance to a desired operating voltage range of the tool. Accordingto an embodiment, the physical design of the motor 202 may be optimizedfor the desired operating voltage range. In an embodiment, optimizingthe motor typically involves increasing or decreasing the stack length,the thickness of the stator windings (i.e., field windings), and lengthof the stator windings. More speed may be provided as the number ofturns of the stator windings is proportionally decreased, though motortorque suffers as a result. To make up for the torque, motor stacklength may be proportionally increased. Also, as the number of turns ofthe stator windings is decreased more space is left in stator slots toproportionally provide thicker stator wires. In other words, thicknessof stator windings may be increased as the number of turns of the fieldwinding is decreased, and vice versa. As the thickness of the statorwindings is increased, motor resistance also decreases. Motor power(i.e., maximum cold power output) is a function of the resistance andthe motor voltage (i.e., back EMF of the motor). Thus, as thickness ofthe stack length and winding thickness is increased and the number ofturns is decreased, motor power is increased for a given input voltage.

In an embodiment, these changes in motor characteristics may be utilizedto improve the performance of the power tool 128 with a lower ratedpower supply to match a desired tool performance. In other words, thevoltage ranging range of the motor 202 is increased in this manner tocorrespond to an operating voltage range of the power tool 128. In anexemplary embodiment, where the DC power supply has a lower nominalvoltage than the AC power supply, modifying these design characteristicsof the motor may be used to double the maximum cold power output of thepower tool operating with a 60V DC power supply, for example, from 850 Wto approximately 1700 W. In an embodiment, motor control unit 208 maythen be configured to reduce the optimal performance of the power tool128 with AC power to match the desired tool performance. This may bedone via any of the techniques described in the next section below.

4. PWM Control Technique for Optimizing Motor Performance Based on PowerSupply

FIG. 11A depicts an exemplary waveform diagram for a drive signal (i.e.,any of UH, VH, or WH drive signals associated with the high-sideswitches) outputted by the controller 230 within a single conductionband of a corresponding phase (i.e., U, V, or H) of the motor. In theillustrated example, the drive signal is being modulated at 100% dutycycle, 80% duty cycle, 50% duty cycle, 20% duty cycle, and 0% dutycycle, for illustration. In this manner, controller 230 controls a speedof the motor 202 based on the variable-speed signal it receives from thevariable-speed actuator (as previously discussed) to enablevariable-speed operation of the motor 202 at constant load.

In order to optimize (i.e., lower) the effective performance of themotor 202 when powered by a higher rated voltage power supply, in anembodiment of the invention, the effective nominal voltage (and thussupply of power to the motor) of the higher rated voltage power supplymay be reduced via a PWM control technique. In an embodiment, thecontrol unit 208 may be configured to control a switching operation ofpower switch circuit 226 at a lower PWM duty cycle when receiving powerfrom a high rated voltage power supply, as previously discussed withreference to FIGS. 7A, 7B, 9A and 9B.

For example, in an embodiment where motor 202 is designed to operate ata voltage range of 60V to 90V but receives AC power from a power supplyhaving a nominal voltage in the range of 100-120V, the control unit 208may be configured to set a maximum PWM duty cycle of the PWM switchcircuit 226 components at a value in the range of 60% to 80% (e.g., 70%)when operating from motor 202 from the AC power line. In another examplewhere motor 202 is designed to operate at a voltage range of 100V to120V, or more broadly 90V to 130V, but receive AC power from a powersupply having a nominal voltage in the range of 220V to 240V, thecontrol unit 208 may be configured to set a maximum PWM duty cycle ofthe PWM switch circuit 226 components at a value in the range of 40% to60% (e.g., 50%) when operating the motor 202 from the AC power line. Thecontrol unit 208 accordingly performs PWM control on the modulated ACsupply (hereinafter referred to as the DC bus voltage, which is thevoltage measured across the capacitor 224) proportionally from 0% up tothe maximum PWM duty cycle.

In an exemplary embodiment, if the maximum duty cycle is set to 50%, thecontrol unit 208 turns the drive signal UH, VH, or WH on the DC bus lineON at 0% duty cycle at no speed, to 25% duty cycle at half speed, and upto 50% duty cycle at full speed.

It is noted that any of the other method previously discussed withreference to power tools 123-126 (e.g., use of a half-wave dioderectifier bridge) may be additionally or alternatively utilized to lowerthe effective nominal voltage provided by the AC power supply to thepower switch circuit 226.

It is further noted that the PWM control technique for motor performanceoptimization discussed above may be used in combination with the othertechniques discussed later in this disclosure in order to obtainsomewhat comparable speed and power performance from the motor 202irrespective of the power supply voltage rating.

It is further noted that in some power tool applications, the PWMcontrol scheme discussed herein may be applicable to both powersupplies. Specifically, for power tool applications such as small anglegrinders with a maximum power output of 1500 W, it may be desirable tooptimize (i.e., lower) the effective performance of the motor 202 whenpower by either a 120V AC power supply (wherein the maximum PWM dutycycle may be set to, e.g., 50%), or a 72V DC power supply (wherein themaximum PWM duty cycle may be set to, e.g., 75%).

5. Current Limit for Optimization of Motor Performance Based on PowerSupply

According to an embodiment of the invention, in order to optimize (i.e.,lower) the effective performance of the motor 202 when powered by ahigher voltage power supply, the motor control unit 208 may beconfigured to use a current limiting technique discussed herein.

In an embodiment, control unit 208 may impose a cycle-by-cycle currentlimit to limit the maximum watts out of the motor 202 when operating ahigher rated voltage power supply to match or fall within theperformance of associated with the operating voltage range of the motor202. When the instantaneous bus current in a given cycle exceeds aprescribed current limit, the drive signals to the switches in the PWMswitch circuit 226 are turned off from the remainder of the cycle. Atthe beginning of the next cycle, the drive signals are restored. Foreach cycle, the instantaneous current continues to be evaluated in asimilar manner. This principle is illustrated in FIG. 11B, where thesolid line indicates the instantaneous current without a limit and thedash line indicates the instantaneous current with a 20 amp limit.Cycle-by-cycle current limit enables the power tool to achieve similarperformance across different types of power supplies and under varyingoperating conditions as will be further described below.

Cycle-by-cycle current limiting can be implemented via a current sensor(not shown) disposed on the DC bus line and coupled to the controller230. Specifically, a current sensor is configured to sense the currentthrough the DC bus and provide a signal indicative of the sensed currentto the controller 230. In an exemplary embodiment, the current sensor isimplemented using a shunt resistor disposed in series between therectifier 222 and the PWM switch circuit 226. Although not limitedthereto, the shunt resistor may be positioned on the low voltage side ofthe DC bus. In this way, the controller 230 is able to detect theinstantaneous current passing through the DC bus.

The controller 230 is configured to receive a measure of instantaneouscurrent passing from the rectifier to the switching arrangement operatesover periodic time intervals (i.e., cycle-by-cycle) to enforce a currentlimit. With reference to FIG. 11C, the controller 230 enforces thecurrent limit by measuring current periodically (e.g., every 5microseconds) at 290 and comparing instantaneous current measures to thecurrent limit at 291. If the instantaneous current measure exceeds thecurrent limit, the controller 230 deactivates power switch circuit 226switches at 292 for remainder of present time interval and therebyinterrupts current flowing to the electric motor. If the instantaneouscurrent measure is less than or equal to the current limit, thecontroller 230 continues to compare the instantaneous current measuresto the current limit periodically for the remainder of the present timeinterval as indicated at 293. In an embodiment, such comparisons occurnumerous times during each time interval (i.e. cycle). When the end ofthe present time interval is reached, the controller 230 reactivatespower switch circuit 226 switches at 294 and thereby resumes currentflow to the motor for the next cycle. In one embodiment, the duration ofeach time interval is fixed as a function of the given frequency atwhich the electric motor is controlled by the controller 230. Forexample, the duration of each time interval is set at approximately tentimes an inverse of the frequency at which the electric motor iscontrolled by the controller. In the case the motor is controlled at afrequency of 10 kilohertz, the time interval is set at 100 microseconds.In other embodiments, the duration of each time interval may have afixed value and no correlation with the frequency at which the electricmotor is controlled by the controller.

In the example embodiment, the each time interval equals period of thePWM signals. In a constant speed tool under a no load (or constant load)condition, the duty cycle of the PWM drive signals is set, for exampleat 60%. In an embodiment, under load, the controller 230 operates tomaintain a constant speed by increasing the duty cycle. If the currentthrough the DC bus line increases above the current limit, thecontroller 230 interrupts current flow as described above which ineffect reduces the duty cycle of the PWM signals. For a variable speedtool under a no load condition, the duty cycle of the PWM drive signalsranges for example from 15% to 60%, in accordance with user controlledinput, such as a speed dial or a trigger switch. The controller 230 canincrease or decrease the duty cycle of the PWM signals during a loadcondition or an over current limit condition in the same manner asdescribed above. In one embodiment, speed control and current limitingmay be implemented independently from each other by using three upperhigh-side power switches for speed control and the three low-side powerswitches for current limiting. It is envisioned that the two functionsmay be swapped between the upper and lower switches or combined togetherinto one set of switches.

In the examples set forth above, the time interval remained fixed. Whenthis period (time interval) remains fixed, then the electronic noisegenerated by this switching will have a well-defined fundamentalfrequency as well as harmonics thereof. For certain frequencies, thepeak value of noise may be undesirable. By modulating the period overtime, the noise is distributed more evenly across the frequencyspectrum, thereby diminishing the noise amplitude at any one frequency.In some embodiment, it is envisioned that the direction of the timeinterval may be modulated (i.e., varied) over time to help distributeany noise over a broader frequency range.

In another embodiment, controller 230 enforces the cycle-by-cyclecurrent limit by setting or adjusting the duty cycle of the PWM drivesignals output from the gate driver circuit 232 to the power switchcircuit 226. In an embodiment, the duty cycle of the PWM drive signalsmay be adjusted in this manner following the instant current cycle(i.e., at the beginning of the next cycle). In a fixed speed tool, thecontroller 230 will initially set the duty cycle of the drive signals toa fixed value (e.g., duty cycle of 75%). The duty cycle of the drivesignals will remain fixed so long as the current through the DC busremains below the cycle-by-cycle current limit. The controller 230 willindependently monitor the current through the DC bus and adjust the dutycycle of the motor drive signals if the current through the DC busexceeds the cycle-by-cycle current limit. For example, the controller230 may lower the duty cycle to 27% to enforce the 20 amp current limit.In one embodiment, the duty cycle value may be correlated to aparticular current limit by way of a look-up table although othermethods for deriving the duty cycle value are contemplated by thisdisclosure. For variable speed tool, the controller 230 controls theduty cycle of the motor drive signals in a conventional manner inaccordance with the variable-speed signal from the variable-speedactuator. The cycle-by-cycle current limit is enforced independently bythe controller 230. That is, the controller will independently monitorthe current through the DC bus and adjust the duty cycle of the drivesignals only if the current through the DC bus exceeds thecycle-by-cycle current limit as described above.

In one embodiment, the cycle-by-cycle current limit is dependent uponthe type and/or nominal voltage of the power supply. In an embodiment,depending on the nominal voltage of the AC or DC power supply, thecontroller 230 selects a current limit to enforce during operation ofthe power tool. In one embodiment, the current limit is retrieved by thecontroller 230 from a look-up table. An example look-up table is asfollows:

Source type Nominal voltage Current limit AC 120 V 40 A AC 230 V 20 A DC120 V 35 A DC 108 V 40 A DC 60 V 70 A DC 54 V 80 A

That is, in this exemplary embodiment, in a motor 202 having anoperating voltage range of 100V to 120V, the controller 230 will enforcea 40 amp current limit when the tool is coupled to a 120V AC powersupply but will enforce a 20 amp current limit when the tool is coupledto a 230V AC power supply. As a result, the effective output power ofthe tool is substantially the same. In an alternative embodiment wherethe power tool has an operating voltage range of 150V to 170V,controller 230 may enforce a 30 A current limit in order to reduce theeffective performance of the motor 202 when powered by the 230V AC powersupply.

Further, controller 230 is configured to enforce a 40 am current limitwhen the tool is coupled to a 108V DC power supply, but will enforce aslightly lower current limit (e.g., 35 amps) when the tool is coupled toa 120V DC power supply (e.g., when the tool is being supplied DC powerfrom a generator or a welder). Similarly, controller 230 is configuredto enforce a 80 am current limit when the tool is coupled to a 54V DCpower supply, but will enforce a slightly lower current limit (e.g., 70amps) when the tool is coupled to a 60V DC power supply. These currentlimits result in output power levels from the AC or DC power supplies toall be compatible with a motor 202 having an operating voltage range of100V to 120V.

Further details for cycle-by-cycle current limiting and its applicationsare discussed in U.S. Provisional Application No. 62/000,307, filed May19, 2014, titled “Cycle-By-Cycle Current Limit For Power Tools Having ABrushless Motor,” and related U.S. Utility Patent Application No.14/715,079, filed May 18, 2015, now U.S. Pat. No. 9,762,153, having thesame title, each of which is incorporated herein by reference in itsentirety.

It is noted that the cycle-by-cycle current limiting technique foroptimization of motor performance discussed above may be used incombination any other motor performance optimization technique discussedin this disclosure in order to obtain somewhat comparable speed andpower performance from the motor 202 irrespective of the power supplyvoltage rating.

6. Conduction Band and/or Advance Angle Control for Adjusting MotorPerformance Based on Power Supply

According to an embodiment of the invention, in order to optimize (i.e.,boost or enhance) the effective performance of the motor 202 whenpowered by a higher rated voltage power supply, the control unit 208 maybe configured to use a technique involving the conduction band and/orthe advance angle (herein referred to as “CB/AA technique”) describedherein.

FIG. 12A depicts an exemplary waveform diagram of a pulse-widthmodulation (PWM) drive sequence of the three-phase inventor bridgecircuit FIG. 10C within a full 360 degree conduction cycle. As shown inthis figure, within a full 360° cycle, each of the drive signalsassociated with the high-side and low-side power switches is activatedduring a 120° conduction band (“CB”). In this manner, each associatedphase of the BLDC 202 motor is energized within a 120° CB by apulse-width modulated voltage waveform that is controlled by the controlunit 208 as a function of the desired motor 202 rotational speed. Foreach phase, UH is pulse-width modulated by the control unit 208 within a120° CB. During the CB of the high-side switch, the corresponding UL iskept low. The UL signal is then activated for a full 120° CB within ahalf cycle (180°) after the CB associated with the UL signal. Thecontrol unit 208 controls the amount of voltage provided to the motor,and thus the speed of the motor, via PWM control of the high-sideswitches.

It is noted that while the waveform diagram of FIG. 12A depicts oneexemplary PWM technique at 120° CB, other PWM methods may also beutilized. One such example is PWM control with synchronousrectification, in which the high-side and low-side switch drive signals(e.g., UH and UL) of each phase are PWM-controlled with synchronousrectification within the same 120° CB.

FIG. 12B depicts an exemplary waveform diagram of the drive sequence ofthe three-phase inventor bridge discussed above operating at full-speed(i.e., maximum speed under constant-load condition). In this figure, thethree high-side switches conduct at 100% PWM duty cycle during theirrespective 120° CBs, providing maximum power to the motor to operate atfull-speed.

In a BLDC motor, due to imperfections in the commutation of the powerswitches and the inductance of the motor itself, current will slightlylag behind the back-EMF of the motor. This causes inefficiencies in themotor torque output. Therefore, in practice, the phase of the motor isshifted by an advance angle (“AA”) of several degrees so the currentsupplied to the motor no longer lags the back-EMF of the motor. AArefers to a shifted angle Y of the applied phase voltage leading ahead arotational EMF of the corresponding phase.

In addition, in an embodiment, the motor 202 may be aninterior-permanent magnet (IPM) motor or other salient magnet motor.Salient magnet motors can be more efficient than surface-mount permanentmagnet motors. Specifically, in addition to the magnet torque, a salientmagnet motor includes a reluctance torque that varies as a function ofthe motor current (specifically, as a function of the square of themotor current), and therefore lags behind the magnet torque. In order totake advantage of this reluctance torque, in an embodiment, the AAshifted angle Y is increased to encompass the lag of the reluctancetorque. The added reluctance torque enables the salient magnet motor toproduce 15 percent or more torque per amp than it would without thefurther shift in angle Y.

In an embodiment, AA may be implemented in hardware, where positionalsensors are physically shifted at an angle with respect to the phase ofthe motor. Alternatively or additional, AA may be implanted in software,where the controller 230 is configured to advance the conduction band ofeach phase of the motor by the angle Y, as discussed herein.

FIG. 12C depicts the waveform diagram of the drive sequence of FIG. 12B,shown with an AA of Y=30°, according to an embodiment. In an embodiment,AA of 30 degrees is sufficient (and is commonly used by those skilled inthe art) in BLDC applications to account for the current lag withrespect to the back-EMP of the motor and take advantage of thereluctance torque of salient magnet motors.

According to an embodiment, increasing the AA to a value greater thanY=30° can result in increased motor speed performance. FIG. 12D depictsa speed/torque waveform diagram of an exemplary power tool 128, whereincreasing the AA at a fixed CB of 120° results in an upward shift inthe speed/torque profile, i.e., from 252 (Y=30°), to 253 (Y=40°), to 254(Y=50°). This shift is particularly significant at a low torque range(e.g., 0 to 1 N.m.), where motor speed can increase by approximately 20%from 252 to 253, and even more from 253 to 254 (particularly at very lowtorque range of, e.g., 0.2 N.m. where the speed can more than double).At a medium torque range (e.g., 1 to 2 N.m.), the increase in motorspeed is noticeable, but not significant. At a high torque range (e.g.,2 N.m. and above), the increase in motor speed is minimal.

Similarly, increasing the AA to a value greater than Y=30° can result inincreased power output. FIG. 12E depicts a power-out/torque waveformdiagram of exemplary tool 128, where increasing the AA at fixed CB of120° results in an upward shift in the power-out/torque profile, i.e.,from 255 (AA=30°), to 256 (AA=40°), to 257 (AA=50°). This shift issomewhat significant at the low and medium torque range of, for example,up to 20% at approximately 1 N.m., but does not have a considerableeffect on power output at the high torque range.

While not depicted in these figures, it should be understood that withinthe scope of this disclosure and consistent with the figures discussedabove, power output and speed performance may similarly be reduced if AAis set to a value lower than Y=30° (e.g., Y=10° or 20°).

According to an embodiment of the invention, in order to optimize theeffective performance of the motor 202 when tool 128 is powered by apower supply that has a nominal (or rated) voltage that is higher orlower than the operating voltage of the motor 202, the AA for the phasesof the motor 202 may be set according to the voltage rating or nominalvoltage of the power supply. Specifically, AA may be set to a highervalue in order to boost the performance of the motor 202 when powered bya lower rated voltage power supply, and set to a lower value in order toreduce the performance of the motor 202 when powered by a higher ratedvoltage power supply, so that somewhat equivalent or comparable speedand power performance is obtained from the motor 202 irrespective of thepower supply voltage rating. For example, in an embodiment, control unit208 may be configured to set AA of Y=30° when power supply has a nominalvoltage that falls within or matches the operating voltage range of themotor 202 (e.g., 70-90V), but set AA to a higher value (e.g., Y=50°)when power tool 128 is coupled to a lower rated voltage power supply(e.g., 54 VDC), and/or set AA to a lower value (e.g., Y=20°) when powertool 128 is coupled to a higher rated voltage power supply (e.g., 120VAC). In an embodiment, control unit 208 may be provided with a look-uptable or an equation defining a functional relationship between AA andthe power supply voltage rating.

While increasing AA to a value greater than Y=30° may be used to boostmotor speed and power performance, increasing the AA alone at a fixed CBcan result in diminished efficiency. As will be understood by thoseskilled in the art, efficiency is measured as a function of(power-out/power-in). FIG. 12F depicts an exemplary efficiency/torquewaveform diagram of tool 128, where increasing the AA at fixed CB of120° results in a downward shift in the efficiency/torque profile, i.e.,from 258 (Y=30°), to 259 (Y=40°), to 265 (Y=50°). This shift isparticularly significant at low torque range, where efficiency candecrease by, for example, approximately 20% at around 0.5 N.m., and evenmore at lower torque. In other words, while increasing the AA alone (atfixed CB) to a value greater than Y=30° can increase speed and poweroutput at low and medium torque ranges, it does so by significantlysacrificing tool efficiency.

It was found by the inventors of this application that increasing the CBfor each phase of a BLDC motor increases total power output and speed ofthe motor 208, particularly when performed in tandem with AA, asdiscussed herein.

Turning to FIG. 13A, a waveform diagram of the drive sequence of thethree-phase inventor bridge of the power switch circuit 226 previouslydiscussed is depicted, with a CB value greater than 120°, according toan embodiment of the invention. In an embodiment, the CB of each phaseof the brushless motor may be increased from 120°, which is the CB valueconventionally used by those skilled in the art, to, for example, 150°as shown in this illustrative example. As compared to a CB of 120° shownin FIG. 12A, the CB may be expanded by 15° on each end to obtain a CB of150°. Increasing the CB to a value greater than 120° allows three of theswitches in the three-phase inventor bridge to be ON simultaneously(e.g., between 45° to 75° and 105° to 135° in the illustrative example)and for voltage to be supplied to each phase of the motor during alarger conduction period. This, in effect, increases the total voltageamount being supplied to the motor 202 from the DC bus line, whichconsequently increases the motor speed and power output performance, asdiscussed below.

FIG. 13B depicts an embodiment of the invention where the AA of eachphase of the brushless motor is also varied in tandem with andcorresponding to the CB. In the illustrative example, where the CB is at150°, the AA is set to an angle of Y=45°. In an embodiment, various CBand AA correlations may be implemented in controller 230 as a look-uptable or an equation defining a functional relationship between CB andthe associated AA.

An exemplary table showing various CB and associated AA values is asfollows:

CB AA (γ) 120° 30° 130° 35° 140° 40° 150° 45° 160° 50° 170° 55°

It is noted that while these exemplary embodiments are made withreference to CB/AA levels of 120°/30°, 140°/40°, 160°/50°, these valuesare merely exemplary and any CB/AA value (e.g., 162°/50.6°, etc.) may bealternatively used. Also, the correlation between AA and CB provides inthis table and throughout this disclosure is merely exemplary and not inany way limiting. Specifically, while the relationship between CB and AAin the table above is linear, the relationship may alternatively benon-linear. Also, the AA values given here for each CB are by no meansfixed and can be selected from a range. For example, in an embodiment,CB of 150° may be combined with any AA in the range of 35° to 55°,preferably in the range of 40° to 50°, preferably in the range of 43° to47°, and CB of 160° may be combined with any AA in the range of 40° to60°, preferably in the range of 45° to 55°, preferably in the range of48° to 52°, etc. Moreover, optimal combinations of CB and AA may varywidely from the exemplary values provided in the table above in somepower tool applications.

Referring now to FIGS. 13C and 13D, increasing the CB and AA in tandem(hereinafter referred to as “CB/AA”) as described above to a levelgreater than the CB/AA of 120°/30° can result in better speed and poweroutput performance over a wider torque range as compared to the waveformdiagrams of FIGS. 12D and 12E, according to an embodiment.

As shown in the exemplary speed/torque waveform diagram of FIG. 13C fortool 128, increasing CB/AA results in a significant upward shift in thespeed/torque profile, i.e., from 262 (CB/AA=120°/30°), to 263(CB/AA=140°/40°), to 264 (CB/AA=160°/50°), according to an embodiment.This increase is the greatest at the low torque range (where speedperformance can improve by at least approximately 60%), but stillsignificant at the medium torque range (where speed performance canimprove by approximately 20% to 60%). It is noted that in an embodiment,the speed/torque profiles 262, 263, 264 begin to converge at a very lowspeed/very high torque range (e.g., between 7,000 rpm to 10,000 rpm),after which point increasing CB/AA no longer results in better speedperformance.

Similarly, as shown in the exemplary power-out/torque waveform diagramof FIG. 13D for tool 128, increasing CB/AA results in a significantupward shift in the power-out/torque profile, i.e., from 265(CB/AA=120°/30°), to 266 (CB/AA=140°/40°), to 267 (CB/AA=160°/50°),according to an embodiment. In an embodiment, this increase is thegreatest from 266 (CB/AA=140°/40°) to 267 (CB/AA=160°/50°) at the lowtorque range and from 265 (CB/AA=120°/30°) to 266 (CB/AA=140°/40°) atmedium and high torque ranges. It is noted that in this figure theincrease in CB/AA from 120°/30°) to 160°/50° may yield an increase of upto 50% for some torque conditions, though the motor maximum power output(measured at very high load at max speed) may be increased by 10-30%.

While not depicted in these figures, it should be understood that withinthe scope of this disclosure and consistent with the figures discussedabove, power output and speed performance may similarly be reduced ifCB/AA is set to a lower level (e.g., 80°/10° or 100°/20°) than 120°/30°.

According to an embodiment of the invention, in order to optimize theeffective performance of the motor 202 when tool 128 is powered by apower supply that has a nominal (or rate) voltage that is higher orlower than the operating voltage of the power tool 128, the CB/AA forthe phases of the motor 202 may be set according to the voltage ratingor nominal voltage of the power supply. Specifically, CB/AA may be setto a higher value in order to boost the performance of the motor 202when powered by a lower rated voltage power supply, and set to a lowervalue in order to reduce the performance of the motor 202 when poweredby a higher rated voltage power supply, so that somewhat comparablespeed and power performance is obtained from the motor 202 irrespectiveof the power supply voltage rating.

In an embodiment, control unit 208 may be configured to set CB/AA to120°/30° when power supply has a nominal voltage that corresponds to theoperating voltage range of the motor 202, but set CB/AA to a higherlevel when coupled to a lower rated voltage power supply. Similarly,control unit 208 sets CB/AA to a lower level when coupled to a higherrated voltage power supply. For example, for a motor 202 having anoperating voltage range of 70V-90V, control unit 208 may be configuredto set CB/AA to 120°/30° for a 72 VDC or 90 VDC power supply, but to,e.g., 140°/40° for a 54 VDC power supply and to 100°/20° for a 120 VACpower supply. In another example, for a motor 202 having an operatingvoltage range of 90V to 132V, control unit 208 may be configured to setCB/AA to 120°/30° for a 120 VAC power supply, but to proportionallyhigher values, e.g., 160°/50° and 140°/40° respectively for a 54 VDCpower supply and a 72 VDC power supply. In yet another example, for amotor 202 having an operating voltage range of 135V to 187V, controlunit 208 may be configured to set CB/AA to, e.g., 140°/40° for a 108 VDCpower supply or a 120 VAC power supply, and to 100°/20° for a 220 VACpower supply. In an embodiment, control unit 208 may be provided with alook-up table or an equation defining a functional relationship betweenCB/AA and the power supply voltage rating.

In an embodiment, the CB/AA control technique described herein may beused in combination with any of the other motor optimization techniquesdisclosed in this disclosure. For example, the CB/AA control techniquemay be used to boost the performance of the motor 202 when powered by alower rated voltage power supply, and the PWM control techniquediscussed above, or the cycle-by-cycle current limiting techniquediscussed above, or a combination of both, may be used to lower theperformance of the motor 202 when powered by a higher rated voltagepower supply, so that somewhat comparable speed and power performance isobtained from the motor 202 irrespective of the power supply voltagerating. However, in an embodiment, it may be advantageous to utilize theCB/AA technique described above over the PWM control technique to lowerperformance of the motor for a higher rated voltage power supply,particularly for constant-speed power tool applications. This is becausePWM switching of the power switches generates heat and increases thevoltage harmonic factor. Use of the CB/AA technique described mitigatesthose effects on heat and voltage harmonics.

It is noted that while the description above is directed to adjusting CBin tandem with AA based on power supply rated voltage, adjusting CBalone (i.e., at a fixed AA level) according to the power supply ratedvoltage is also within the scope of this disclosure. Specifically, justas varying the AA level at constant CB has an effect on power and speedperformance at certain torque ranges (as described above with referenceto FIGS. 12D-12F), varying the CB level above and below 120 degrees atconstant AA can also increase or decrease total voltage supplied to themotor, and therefore enhance or decrease motor speed and power output,tool efficiency may be sacrificed in certain torque ranges. Accordingly,in an embodiment of the invention, where tool 128 is powered by a powersupply that has a nominal (or rated) voltage that is higher or lowerthan the operating voltage of the motor 202, the effective motorperformance may be optimized by adjusting the CB (at constant AA) forthe phases of the motor 202 according to the voltage rating or nominalvoltage of the power supply. Specifically, CB may be set to a highervalue than 120 degrees in order to boost the performance of the motor202 when powered by a lower rated voltage power supply, and set to alower value in order to reduce the performance of the motor 202 whenpowered by a higher rated voltage power supply, so that somewhatequivalent speed and power performance is obtained.

It is also once again reiterated that CB/AA levels of 120°/30°,140°/40°, 160°/50° mentioned in any of these embodiments (as well as theembodiments discussed below) are merely by way of example and any otherCB/AA level or combination that result in increased power and/or speedperformance in accordance with the teachings of this disclosure arewithin the scope of this disclosure.

It is also noted that all the speed, torque, and power parameters andranges shown in any of these figures and discussed above (as we as thefigures and embodiments discussed below) are exemplary by nature and arenot limiting on the scope of this disclosure. While some power tools mayexhibit similar performance characteristics shown in these figures,other tools may have substantially different operational ranges.

7. Improved Torque-Speed Profile

Referring now to FIG. 13E, an exemplary efficiency/torque diagram oftool 128 is depicted with various CB/AA values at 268 (CB/AA=120°/30°),269 (CB/AA=140°/40°) and 270 (CB/AA=160°/50°), according to anembodiment. As can be seen in this figure, CB/AA of 120°/30° yields thebest efficiency at approximately a low to medium range (e.g., 0 toapproximately 1.5 N.m. in the illustrative example), CB/AA of 140°/40°yields the best efficiency at approximately a medium to high torquerange (approximately 1.5 N.m. to approximately 2.5 N.m. in theillustrative example), and CB/AA of 160°/50° yields the best efficiencyat approximately a high torque range (approximately above 2.5 N.m. inthe illustrative example). Accordingly, while increasing CB/AA beyond120°/30° level greatly improves speed and power performance at alltorque ranges, it may do so to the detriment of efficiency in someoperating conditions, particularly at relative low torque ranges.

In addition, power tools applications generally have a top rated speed,which refers to the maximum speed of the power tool motor at no load. Invariable-speed tools, the maximum speed typically corresponds to adesired speed that the motor is designed to produce at full triggerpull. Also, the rated voltage or operating voltage (or voltage range) ofthe motor previously discussed corresponds to the power tool's desiredtop rated speed. The motor's physical characteristics previouslydiscussed (e.g., size, number of windings, windings configuration, etc.)are also generally designed to be compatible with the power tool'storque and maximum speed requirements. In fact, it is often necessary toprotect the motor and the power tool transmission from exceeding the toprated speed. In a tool where the motor has the capability to output morespeed than the tool's top rated speed, the speed of the motor istypically capped at its top rated speed. Thus, while increasing speedperformance via the above-described CB/AA technique is certainlydesirable within some torque/speed ranges, it is impractical in certainoperating conditions if the increased CB/AA causes the motor speed toexceed the top rated speed of the tool. This is particularly true in thelow torque range, where, as previously shown in FIG. 13C, increasingCB/AA creates a very large shift in the speed profile.

In an exemplary embodiment, where tool 128 of FIG. 13C has a top ratedspeed of 25,000 rpm, operating the motor 202 at CB/AA of 120°/30° allowsthe tool to operate within its top rated speed, but operating the toolat a higher CB/AA exceeds the top rated speed at the low torque range(e.g., speed exceeds 25,000 rpm with CB/AA of 160°/50° at under 1 N.m.torque, or with CB/AA of 140°/40° at under 0.6 N.m torque).

Accordingly, in an embodiment of the invention, as shown in FIG. 13F, animproved speed-torque profile is provided, wherein at the top ratedspeed of the tool, the motor speed is held at a constant rate (i.e.,includes a substantially flat profile 280) within a first torque range,e.g., 0 to approximately 1.2 N.m., and at a variable rate within asecond torque range, e.g., above 1.2 N.m. In an embodiment, during thefirst torque range, CB/AA is gradually increased as a function of thetorque from its base value (e.g., 120/30°) to a threshold value (e.g.,160/50°). Once that CB/AA threshold is reached, the speed-torque profilefollows a curved profile 282 of the normal speed-torque profileoperating at a CB/AA corresponding to the threshold value (e.g., profile264 operating at 160/50°). In other words, the speed-torque curve atCB/AA of 160/50° is “clipped” below the tool's maximum speed, which inthis example is 25,000 RPM.

The tool's performance according to this improved speed-torque profileis improved in several regards. First, it avoids operating the motor athigh CB/AA levels of, for example, 160/50° at the low torque range, inparticular at very low torque of under 0.5 N.m. in the exemplaryembodiment where efficiency suffers the most from operating at a highCB/AA (see FIG. 13E above). This dramatically increases motor efficiencyat the low torque range. Also, it gives the users the ability to operatethe tool at maximum speed for a wide range of the operating torque (0 to1.2 N.m. in the exemplary embodiment), which is beneficial to the users.Moreover, the tool operates according to a speed-torque curve at mediumand high torque ranges, which the users generally expect, but at ahigher power output and higher efficiency as described with reference toFIGS. 13D and 13E above. This arrangement thus increases overall toolefficiency and power output.

In order to maintain constant speed at flat portion 280 of thespeed/torque profile, control unit 208 may be configured to operate themotor at variable CB/AA calculated or determined as a function of thetorque from a base CB/AA value (e.g., 120/30°, which corresponds to atorque of slightly above to zero) to a threshold CB/AA value (e.g.,160/50°), as described above. In an embodiment, control unit 208 mayutilize a look-up table or an algorithm to calculate and graduallyincrease the CB/AA as required to achieve the desired constant speed asa function of torque, according to an embodiment. Thereafter, controlunit 208 is configured to operate the motor at constant CB/AAcorresponding to the CB/AA threshold value (e.g., 160/50°), according toan embodiment.

According to an alternative embodiment, the control unit 208 may beconfigured to operate the motor at variable CB/AA calculated as afunction of the torque from a low torque threshold (e.g., zero orslightly above zero, which corresponds to, e.g., CB/AA of 120/30°) to ahigh torque threshold (e.g., 1.2 N.m., which corresponds to, e.g., CB/AAof 160/50°). Again, the control unit 208 may utilize a look-up table oran algorithm to calculate and gradually increase the CB/AA that isrequired to achieve the desired constant speed as a function of thetorque, according to an embodiment. Thereafter, control unit 208 isconfigured to operate the motor at constant CB/AA corresponding to thehigh torque threshold (e.g., 160/50° corresponding to 1.2 N.m.),according to an embodiment.

As discussed with reference to FIG. 13C above, the speed/torque profiles262, 263, 264 begin to converge at a very low speed/very high torquerange (e.g., between 7,000 rpm to 10,000 rpm and around 3 N.m.), afterwhich point increasing CB/AA no longer results in better speedperformance. After that point, speed/torque profiles 262 (120/30° yieldshigher speed performance than higher CB/AA levels. Thus, according to anembodiment, above a high threshold torque value (e.g., 3 N.m. in thisexample) or below a low threshold speed (e.g., approximately 8,500 rpmin this example), the speed/torque profile may revert back from profile282 corresponding to a CB/AA of 160/50° to another profile 284corresponding to a CB/AA of 120/30°, in order to obtain higherperformance at high torque and low speed levels. The control unit 208 inthis embodiment may be configured to reduce the CB/AA from the highthreshold of 160/50° back down to 120/30° once the high threshold torque(or low threshold speed) is reached. This reversion may be doneinstantaneously or gradually to obtain a smooth transition.

FIG. 13G depicts a further improvement to the speed-torque profile ofFIG. 13F, where instead of holding motor speed constant at low torque,motor speed is controlled at a variable rate according to a firstprofile 286 within a first torque range, in this case e.g., 0 toapproximately 1.5 N.m., and according to a second profile 288 within asecond torque range, e.g., above 1.5 N.m. In an embodiment, similar tothe embodiment of FIG. 13F, CB/AA is gradually increased as a functionof the torque from its base value (e.g., 120/30°) to a threshold value(e.g., 160/50°) during the first torque range. Once that CB/AA thresholdis reached, the speed-torque profile follows a curved profile 288 of thenormal speed-torque profile operating at a CB/AA corresponding to thethreshold value (e.g., profile 264 operating at 160/50°). In contrast tothe embodiment of FIG. 13F, however, the increase in CB/AA is designedto gradually reduce speed from the top rated speed down to a secondspeed value, e.g., 12,000 rpm, within the first torque range. Thisconfiguration allows the transition to higher CB/AA levels to occur at aslower rate, which results in further increases in efficiency within thefirst torque range.

It is noted that while the first profile 286 in this embodiment islinear, any other non-linear profile, or any combination of flat,linear, and non-linear profile, may be alternatively employed within thefirst torque range in order to increase efficiency. For example, in anembodiment, first profile 286 may include a steep portion along profile262 (wherein CB/AA is maintained at or around the 120/30° level) for anentire duration of a very small torque range (e.g., 0 to 0.5 N.m.),followed by a flat or semi-flat portion that connects the steep portionto the second profile 282.

According to an embodiment of the invention, the improved speed-torqueprofile described herein may be utilized to optimize the effectiveperformance of the motor 202 with high efficiency when tool 128 ispowered by a power supply that has a nominal (or rate) voltage that ishigher or lower than the operating voltage of the motor 202.Specifically, in an embodiment, instead of operating the motor at aconstant CB/AA level set according to the voltage rating or nominalvoltage of the power supply, CB/AA may be varied at described above tomaximize the motor efficiency. Specifically, in an embodiment, in orderto boost the performance of the motor 202 when powered by a lower ratedvoltage power supply, instead of fixedly setting CB/AA to a higher level(e.g., 160°/50°) to obtain a torque-speed profile as shown in FIG. 13C,variable CB/AA may be partially adapted (e.g., for a low torque range)to obtain a torque-speed profile according to FIG. 13C or FIG. 13D.

In an embodiment, control unit 208 may be configured to set CB/AA to120°/30° when power supply has a nominal voltage that corresponds to theoperating voltage range of the motor 202, but set variable CB/AA asdescribed above for a low torque when coupled to a lower rated voltagepower supply. For example, in a power tool 128 with a motor 202 havingan operating voltage range of 70V-90V, control unit 208 may beconfigured to set CB/AA to 120°/30° for a 72 VDC or 90 VDC power supply,but to variable CB/AA, e.g., 120°/30° up to 140°/40° for a 54 VDC powersupply. In another example, in a power tool 128 having a motor 202 withan operating voltage range of 90V to 132V, control unit 208 may beconfigured to set CB/AA to 120°/30° for a 120 VAC power supply, but tovariable CB/AA, e.g. from 120°/30° up to 160°/50° (or 140°/40° up to160°/50°) for a 54 VDC power supply.

8. Optimization of Conduction Band and Advance Angle for IncreasedEfficiency

FIG. 14A depicts an exemplary maximum power output contour map for powertool 128 based on various CB and AA values measured at a constant mediumspeed of, e.g., approximately 15,000 rpm, according to an embodiment. Itis noted that this medium speed value corresponds to a medium to hightorque values depending on the CB/AA level (e.g., approximately 1.5 N.m.at CB/AA=120°/30°, approximately 1.85 N.m. at CB/AA=140°/40°, andapproximately 2.2 N.m. at CB/AA=160°/50° per FIG. 13C). In this figure,maximum power output gradually decreases from zone ‘a’ (representing maxpower output of approximately 3,500 W or more) to zone ‘h’ (representingmaximum power output of approximately of 200 W or less). It can be seenbased on this exemplary figure that the highest max power output amountfor power tool 128 at medium tool speed (and medium torque) can beobtained at a CB in the optimal range of approximately 150°-180° and AAin the optimal range of approximately 50°-70°.

FIG. 14B depicts an exemplary output efficiency contour map for powertool 128 based on various CB and AA values measured at the same speed,according to an embodiment. In this figure, calculated efficiencygradually decreases from zone ‘a’ (representing ≥90% efficiency) to zone‘h’ (representing ≤10% efficiency). It can be seen based on thisexemplary figure that the highest efficiency for power tool 128 atmedium tool speed (and medium torque) can be obtained at a CB in theoptimal range of approximately 120°-170° and AA in the optimal range ofapproximately 10°-50°.

FIG. 14C an exemplary combined efficiency and max power output contourmap for power tool 128 based on various CB and AA values measured at thesame speed, according to an embodiment. This contour is obtained basedon an exemplary function of ((Efficiency^3)*Power, where the goal ismaximize power output while keeping efficiency at a high level. Thecalculated combined contour in this figure gradually decreases from zone‘a’ to zone ‘I’. It can be seen based on this exemplary contour map thatthe highest combination of efficiency and power output for power tool128 at medium tool speed (and medium torque) can be obtained at a CB inthe range of approximately 158°-172° combined with AA in the range ofapproximately 40°-58° within zone ‘a’.

This figure illustrates that while increasing the CB and AA in tandem aspreviously described provides a simple way to increase speed and powerperformance levels, such increase need not be in tandem. For example,the CB/AA level of 160°/50° provides substantially equivalent combinedefficiency and max power output performance as other CB/AA combinationsthat fall within zone ‘a’ contour, e.g., 170°/40°.

As mentioned above, the optimal CB/AA contour (zone ‘a’) obtained inthis figure correspond to a constant medium speed, e.g., approximately15,000 rpm, and a constant toque, e.g., approximately 2.2 N.m. per FIG.13C. This constant medium speed is proportional to the rated or nominalvoltage of the input power supply. In this particular example, thecombined efficiency and maximum power output contour map was constructedat an input voltage of 120V. Modifying the input voltage to above andbelow 120V results in different optimal CB and AA contours.

FIG. 14D depicts an exemplary diagram showing the optimal CB/AA contoursbased on the various input voltage levels. As shown in this figure, anoptimal CB and AA is approximately in the range of 115° to 135° and 5°to 30° respectively at an input voltage level of approximately 200V;approximately in the range of 140° to 155° and 25° to 40° respectivelyat an input voltage level of approximately 160V; approximately in therange of 165° to 175° and 60° to 70° respectively at an input voltagelevel of approximately 90V; and approximately in the range of 170° to178° and 70° to 76° respectively at an input voltage level ofapproximately 72V. In other words, the optimal CB/AA contours getsmaller (thus providing a narrower combination range) as the inputvoltage decreases from 200V down to 72V. Also, the optimal CB ranges andAA ranges both increase as the input voltages decreases. It is notedthat the contours herein are optimized to output substantiallyequivalent levels of maximum power output at optimal efficiency.

Accordingly, in an embodiment of the invention, the combined efficiencyand power contours described herein may be utilized to optimize theeffective performance of the motor 202 with high maximum power output atoptimal efficiency based on the nominal (or rated) voltage level of thepower supply. Specifically, in an embodiment, the CB/AA values may beselected from a first range (e.g., CB in the range of 158°-172° and AAin the range of 40°-58°) when powered by a 120V power supply, but from asecond range (e.g., CB in the range of 170°-178° and AA in the range of70°-76°) when powered by a 90V power supply to yield optimal efficiencyand power performance at each voltage input level in a mannersatisfactory to the end user, regardless of the nominal voltage providedon the AC or DC power lines.

In an embodiment, control unit 208 may be configured to set CB/AA to120°/30° when power supply has a nominal voltage that corresponds to theoperating voltage range of the motor 202, but set variable CB/AA asdescribed above for a low torque when coupled to a lower rated voltagepower supply. For example, in a power tool 128 with a motor 202 havingan operating voltage range of 70V-90V, control unit 208 may beconfigured to set CB/AA to 120°/30° for a 72 VDC or 90 VDC power supply,but to variable CB/AA, e.g., 120°/30° up to 140°/40° for a 54 VDC powersupply. In another example, in a power tool 128 having a motor 202 withan operating voltage range of 90V to 132V, control unit 208 may beconfigured to set CB/AA to 120°/30° for a 120 VAC power supply, but tovariable CB/AA, e.g. from 120°/30° up to 160°/50° (or 140°/40° up to160°/50°) for a 54 VDC power supply.

9. Optimization of Motor Performance Using the Link Capacitor

FIG. 15A depicts an exemplary waveform diagram of the rectified ACwaveform supplied to the motor control circuit 206 under a loadedcondition, according to an embodiment. References 240 and 242 designatethe full-wave rectified AC waveform as measured across the capacitor 224(hereinafter referred to as the “DC bus voltage”). It is noted that inthis diagram, it is assumed that the tool is operating under a maximumheavy load that the tool is rated to handle.

Reference 240 designates the DC bus voltage waveform under a loadedcondition where capacitor 224 has a small value of, for example 0 to 50microF. In this embodiment, the effect of the capacitor 224 on the DCbus is negligible. In this embodiment, the average voltage supplied fromthe DC bus line to the motor control circuit 206 under a loadedcondition is:

${V({avg})} = {\frac{120*2*\sqrt{2}}{\pi} = {108\mspace{14mu}{VDC}}}$

Reference 204 designates DC bus voltage waveform under a loadedcondition where capacitor 224 has a relatively large value of, forexample, 1000 microF or higher. In this embodiment, the average voltagesupplied from the DC bus line to the motor control circuit 206 isapproaching a straight line, which is:V(avg)=120*√{square root over (2)}=170VD

It can be seen that by selecting the size of the capacitor 224appropriately, an average DC bus voltage can be optimized to a desiredlevel. Thus, for a brushless AC/DC power tool system designed to receivea nominal DC voltage of approximately 108 VDC, a small capacitor 224 forthe rectifier circuit 220 to produce an average voltage of 108V under aloaded condition from an AC power supply having a nominal voltage of 120VAC.

FIGS. 15B-15D highlight yet another advantage of using a smallcapacitor. FIG. 15B, in an embodiment, depicts the voltage waveformusing a large capacitor (e.g., approximately 4,000 microF) and theassociated current waveform under heavy load. FIG. 15C depicts thevoltage waveform using a medium sized capacitor (e.g., approximately1000 microF) and the associated current waveform under heavy load. FIG.15D depicts the voltage waveform using a small capacitor (e.g.,approximately 200 microF) and the associated current waveform underheavy load.

When using a large capacitor as shown in the exemplary waveform diagramof FIG. 15B, the current supplied to the motor is drawn from thecapacitor for a large portion of each cycle. This in effect shrinks theportion of each cycle during which current is drawn from the AC powersupply, which results in large current spikes to occur within eachcycle. For example, to obtain a constant RMS current of 10 A from the ACpower supply, the current level within the small time window increasessubstantially. This increase often results in large current spikes. Suchcurrent spikes are undesirable for two reasons. First, the power factorof the tool becomes low, and the harmonic content of the AC currentbecomes high. Second, for a given amount of energy transferred from theAC source to the tool, the RMS value of the current will be high. Thepractical result of this arrangement is that an unnecessarily large ACcircuit breaker is required to handle the current spikes for a givenamount of work.

By comparison, when using a medium-sized capacitor as shown in FIG. 15C,the current is drawn from AC power supply within each cycle within abroader time window, which provides a lower harmonic content and higherpower factor. Similarly, when using a small capacitor as shown in FIG.15D, current drawn from the capacitor is very small (almost negligible)within each cycle, providing a larger window for current to be drawnfrom the AC power supply. This provides an even lower harmonic contentand a much higher power factor in comparison to FIGS. 15C and 15D. Aswill be discussed later (see FIG. 12 below), through the smallcapacitors provide a lower average voltage to the motor control circuit204, it is indeed possible to obtain a higher power output from a smallcapacitor 224 due to the lower harmonic context and higher power factor.

Another advantage of using a small capacitor is size. Capacitorsavailable in the market have a typical size to capacitance ratio of 1cm³ to 1 uF. Thus, while it is practical to fit a small capacitor (e.g.,10-200 uF) into a power tool housing depending on the power tool sizeand application, using a larger capacitor may create challenges from anergonomics standpoint. For example, a 1000 uF capacitor is approximately1000 cm³ in size. Conventional power tool applications that requirelarge capacitors typically use external adaptors to house the capacitor.In embodiments of the invention, capacitor 224 is small enough to bedisposed within the tool housing, e.g., inside the tool handle.

According to an embodiment of the invention, the power tool 128 of theinvention may be powered by a DC power supply, e.g., a DC generator suchas a welder having a DC output power line, having a DC output voltage of120V. Using a small capacitor 224 value of approximately 0-50 microF,power tool 128 may provide a higher max power out from a DC power supplyhaving an average voltage of 120V, than it would from a 120V AC mainspower supply, which has an average voltage of 108V. As discussed above,using a small capacitor of 0-50 microF, the DC bus voltage resultingfrom a 120V AC mains power supply remains at an average of approximately108V. An exemplary power tool may provide a maximum cold power output ofapproximately 1600 W from the 108V DC bus. By comparison, the same powertool provides a maximum cold power output of more than 2200 W from theDC bus when power is being supplied by the 120V DC power supply. Thisimprovement represents a ratio of 2200/1600=1.37 (which corresponds tothe voltage ratio^3, i.e., (120/108)^3).

According to an embodiment of the invention, it is possible to providecomparable power outputs from the AC and DC power supplies by adjustingthe value of the capacitor 224. FIG. 15E depicts an exemplary combineddiagram showing power output/capacitance, and average DC busvoltage/capacitance waveforms. The x axis in this diagram depictsvarying capacitor value from 0 to 1000 uF. The Y axes respectivelyrepresent the maximum power watts-out (W) of the power tool ranging from0-2500 W, and the average DC bus voltage (V) ranging from 100-180Vrepresented by dotted lines. The three RMS current values represent therated RMS current of the AC power supply. For example, in the US, thewall socket may be protected by a 15 A RMS current circuit breaker. Inthis example, it is assumed that the power tool is operating under heavyload close to its maximum current rating.

As shown in this diagram, for a power tool configured to be powered by a10 A RMS current power supply (i.e., the tool having a current rating ofapproximately 10 A RMS current, or a power supply having a currentrating of 10A RMS current), the average DC bus voltage under heavy loadis in the range of approximately 108-118V for the capacitor range of0-200 uF; approximately 118-133V for capacitor range of 200 to 400 uF;approximately 133-144V for capacitor range of 400-600 uF, etc.

Similarly, for a power tool configured to be powered by a 15 A RMScurrent power supply (i.e., the tool having a current rating ofapproximately 15 A RMS current, or a power supply having a currentrating of 15 A RMS current), the average DC bus voltage under heavy loadis in the range of approximately 108-112V for the capacitor range of0-200 uF; approximately 112-123V for capacitor range of 200 to 400 uF;approximately 123-133V for capacitor range of 400-600 uF, etc.

Similarly, for a power tool configured to be powered by a 20 A RMScurrent power supply (i.e., the tool having a current rating ofapproximately 20 A RMS current, or a power supply having a currentrating of 20A RMS current), the average DC bus voltage under heavy loadis in the range of approximately 108-110V for the capacitor range of0-200 uF; approximately 110-117V for capacitor range of 200 to 400 uF;approximately 117-124V for capacitor range of 400-600 uF, etc.

In an embodiment, in order to provide an average DC bus voltage from theAC mains power supply (e.g., a 108V nominal RSM voltage) that iscomparable to the nominal voltage received from the DC power supply (120VDC), the capacitor value may be adjusted based on the current rating ofthe power tool and the target DC bus voltage. For example, a capacitorvalue of approximately 230 uF may be used for a tool powered by a 10 ARMS current power supply (i.e., the tool having a current rating ofapproximately 10 A RMS current, or configured to be powered by a powersupply having a current rating of 10 A RMS current) to provide anaverage DC bus voltage of approximately 120V from the AC mains. Thisallows for the power tool to provide a substantially similar outputlevels for 120V AC power supply as it would from a 120V DC power supply.

Similarly, a capacitor value of approximately 350 uF may be used for atool powered by a 15 A RMS current power supply (i.e., the tool having acurrent rating of approximately 15 A RMS current, or configured to bepowered by a power supply having a current rating of 15 A RMS current)to provide an average DC bus voltage of approximately 120V from the ACmains. More generally, capacitor may have a value in the range of290-410 uF for a tool powered by a 15 A RMS current power supply toprovide an average voltage substantially close to 120V on the DC busfrom the AC mains. This allows for the power tool to provide asubstantially similar output levels for 120V AC power supply as it wouldfrom a 120V DC power supply.

Finally, a capacitor value of approximately 500 uF may be used for atool powered by a 20 A RMS current power supply (i.e., the tool having acurrent rating of approximately 20 A RMS current, or configured to bepowered by a power supply having a current rating of 20 A RMS current)to provide an average DC bus voltage of approximately 120V from the ACmains. More generally, the capacitor may have a value in the range of430-570 uF for a tool powered by a 20 A RMS current power supply toprovide an average voltage substantially close to 120V on the DC busfrom the AC mains. This allows for the power tool to provide asubstantially similar output levels for 120V AC power supply as it wouldfrom a 120V DC power supply.

III. Example Power Tool System

FIG. 1B illustrates one particular implementation of the power toolsystem 5001, in accordance with the above disclosure, that includes aset of low rated voltage DC power tools 5002, a set of medium ratedvoltage DC power tools 5003, a set of high rated voltage DC power tools5004, a set of high or AC rated voltage AC/DC power tools 5005, a set oflow rated voltage battery packs 5006, a set of low/medium ratedconvertible battery packs 5007, a high rated voltage AC power supply5008, and a low rated voltage battery pack charger 5009.

The low rated voltage battery packs 5006 have a rated voltage range of17V-20V, with an advertised voltage of 20V, an operating voltage rangeof 17V-19V, a nominal voltage of 18V, and a maximum voltage of 20V. Eachof the low rated voltage battery packs includes a power tool interfaceor terminal block that enables the battery pack 5006 to be coupled tothe low rated voltage power tools 5002 and to the low rated voltagebattery chargers 5009. In one implementation, at least some of the lowrated voltage battery packs 5006 were on sale prior to May 18, 2014. Forexample, the low rated voltage battery packs 5006 may include certainones of DEWALT 20V MAX battery packs, sold by DEWALT Industrial Tool Co.of Towson, Md.

The low/medium rated voltage convertible battery packs 5007 areconvertible between a first configuration having a low rated voltage anda higher capacity and a second configuration having a medium ratedvoltage and a lower capacity. In the first configuration, the low ratedvoltage is approximately 17V-20V, with an advertised voltage of 20V, anoperating voltage range of 17V-19V, a nominal voltage of 18V, and amaximum voltage of 20V. The low rated voltage of the convertible batterypacks 5007 corresponds to the low rated voltage of the low rated voltagebattery packs 5006. In the second configuration, the medium ratedvoltage may be approximately 51V-60V, with an advertised voltage of 60V,an operating voltage range of 51V-57V, a nominal voltage of 54V, and amaximum voltage of 60V. For example, the convertible battery packs 5007may be labeled as 20V/60V MAX battery packs to indicate the multiplevoltage ratings of these convertible battery packs 5007.

The convertible battery packs 5007 would not have been available to thepublic or on sale prior to May 18, 2014. Each of the low/medium ratedvoltage battery packs 5007 includes a power tool interface or terminalblock that enables the battery pack 5007 to be coupled to the low ratedvoltage power tools 5002 and to the low rated voltage battery chargers5009 when in the low rated voltage configuration, and to the mediumrated voltage DC power tools 5003, the high rated voltage DC power tools5004, and the AC/DC power tools 5005 when in the medium rated voltageconfiguration.

The AC power supply 5008 has a high rated voltage that corresponds tothe AC mains rated voltage in North America and Japan (e.g., 100V-120V)or to the AC mains rated voltage in Europe, South America, Asia, andAfrica (e.g., 220V-240V).

The low rated voltage DC power tools 5002 are cordless only tools. Thelow rated voltage DC tools 5002 have a rated voltage range ofapproximately 17V-20V, with an advertised voltage of 20V and anoperating voltage range of 17V-20V. The low rated voltage DC power toolsinclude tools that have permanent magnet DC brushed motors, universalmotors, and permanent magnet brushless DC motors, and may includeconstant speed and variable speed tools. The low rated voltage DC powertools may include cordless power tools having relatively low poweroutput requirements, such as drills, circular saws, screwdrivers,reciprocating saws, oscillating tools, impact drivers, and flashlights,among others. The low rated voltage DC rated voltage power tools 5002may include power tools that were on sale prior to May 18, 2014.Examples of the low rated voltage power tools 5002 may include one ormore of the DeWALT® 20V MAX set of cordless power tools sold by DeWALTIndustrial Tool Co. of Towson, Md.

Each of the low rated voltage power tools 5002 includes a single batterypack interface or receptacle with a terminal block for coupling to thepower tool interface of one of the low rated voltage battery packs 5006,or to the power tool interface of one of the convertible low/mediumrated voltage battery packs 5007. The battery pack interface orreceptacle is configured to place or retain the convertible battery pack5007 into its low rated voltage configuration. Thus, the low ratedvoltage power tools 5002 may operate using either the low rated voltagebattery packs 5006 or the convertible low/medium rated voltage batterypacks 5007 in their low rated voltage configuration. This is because the17V-20V rated voltage of the battery packs 5006, 5007 corresponds to the17V-20V rated voltage of low rated voltage the power tools 5002.

The medium rated voltage DC power tools 5003 are cordless only tools.The medium rated voltage DC power tools 5003 have a rated voltage rangeof approximately 51V-60V, with an advertised voltage of 60V and anoperating voltage range of 51V-60V. The medium rated voltage DC powertools include tools that have permanent magnet DC brushed motors,universal motors, and permanent magnet brushless DC motors, and mayinclude constant speed and variable speed tools. The medium ratedvoltage DC power tools may include similar types of tools as the lowrated voltage DC tools 5002 that have relatively higher powerrequirements, such as drills, circular saws, screwdrivers, reciprocatingsaws, oscillating tools, impact drivers and flashlights. The mediumrated voltage tools 5003 may also or alternatively have other types oftools that require higher power or capacity than the low rated voltageDC tools 5002, such as chainsaws (as shown in the figure), stringtrimmers, hedge trimmers, lawn mowers, nailers and/or rotary hammers.The medium rated voltage DC rated voltage power tools 3 do not includepower tools that were on sale prior to May 18, 2014.

Each of the medium rated voltage DC power tools 5003 includes a singlebattery pack interface or receptacle with a terminal block for couplingto the power tool interface of the convertible low/medium rated voltagebattery packs 5007. The battery pack interface or receptacle isconfigured to place or retain the convertible battery pack 5007 in amedium rated voltage configuration. Thus, the medium rated voltage powertools 5003 may operate using the convertible low/medium rated voltagebattery packs 5007 in the medium rated voltage configuration. This isbecause the 51V-60V rated voltage of the battery packs 5007 correspondsto the 51V-60V rated voltage of medium rated voltage power tools 5003.

The high rated voltage DC power tools 4 are cordless only tools. Thehigh rated voltage DC tools 5004 have a rated voltage range ofapproximately 100V-120V, with an advertised voltage of 120V and anoperating voltage range of 100V-120V. The high rated voltage DC powertools include tools that have permanent magnet DC brushed motors,universal motors, and permanent magnet brushless DC motors, and mayinclude constant speed and variable speed tools. The medium ratedvoltage DC power tools may include tools such as drills, circular saws,screwdrivers, reciprocating saws, oscillating tools, impact drivers,flashlights, string trimmers, hedge trimmers, lawn mowers, nailersand/or rotary hammers. The high rated DC power tools may also oralternatively include other types of tools that require higher power orcapacity such as rotary hammers (as shown in the figure), miter saws,chain saws, hammer drills, grinders, and compressors. The high ratedvoltage DC rated voltage power tools 4 do not include power tools thatwere on sale prior to May 18, 2014.

Each of the high rated voltage DC power tools 5004 includes a batterypack interface having a pair of receptacles each with a terminal blockfor coupling to the power tool interface of convertible low/medium ratedvoltage battery packs 5007. The battery pack receptacles are configuredto place or retain the convertible battery packs 5007 into their mediumrated voltage configurations. The power tools 5004 also include aswitching circuit (not shown) to connect the two battery packs 5007 toone another and to the tool in series, so that the voltages of thebattery packs 5007 are additive. The high rated voltage power tools 5004may be powered by and operate with the convertible low/medium ratedvoltage battery packs 5007 in their medium rated voltage configuration.This is because the two battery packs 5007, being connected in series,together have a rated voltage of 102V-120V (double that of a singlebattery pack 7), which corresponds to the 100V-120V rated voltage ofhigh rated voltage power tools 5004.

The high rated voltage AC/DC power tools 5005 are corded/cordless tools,meaning that they can be powered by either the AC power supply 5008 orthe convertible low/medium rated voltage battery packs 5007. The highrated voltage AC/DC tools 5005 have a rated voltage range ofapproximately 100V-120V (and perhaps as large as 90V-132V), with anadvertised voltage of 120V and an operating voltage range of 100V-120V(and perhaps as large as 90V-132V). The high rated voltage AC/DC powertools 5005 include tools that have universal motors or brushless motors(e.g., permanent magnet brushless DC motors), and may include constantspeed and variable speed tools. The high rated voltage AC/DC power tools5005 may include tools such as drills, circular saws, screwdrivers,reciprocating saws, oscillating tools, impact drivers, flashlights,string trimmers, hedge trimmers, lawn mowers, nailers and/or rotaryhammers. The high rated DC power tools may also or alternatively includeother types of tools that require higher power or capacity such as mitersaws (as shown in the figure), chain saws, hammer drills, grinders, andcompressors. The high rated voltage AC/DC rated voltage power tools 5004do not include power tools that were on sale prior to May 18, 2014.

Each of the high rated voltage AC/DC power tools 5005 includes a powersupply interface having a pair of battery pack receptacles and an ACcord or receptacle. The battery pack receptacles each have a terminalblock for coupling to the power tool interface of one of the convertiblelow/medium rated voltage battery packs. The battery pack receptacles areconfigured to place or retain the convertible battery packs 5007 intheir medium rated voltage configurations. The AC cord or receptacle isconfigured to receive power from the AC power supply 5008. The powertools 5005 include a switching circuit (not shown) configured to selectbetween being powered by the AC power supply 5008 or the convertiblebattery packs 5007, and to connect the two convertible battery packs5007 to one another and to the tool in series, so that the voltages ofthe battery packs 5007 are additive. The high rated voltage AC/DC powertools 5005 may be powered by and operate with two convertible low/mediumrated voltage battery packs 5007 in their medium rated voltageconfiguration, or with the AC power supply 5008. This is because the twobattery packs 5007, being connected in series, together have a ratedvoltage of 102V-120V (double that of a single battery pack 5007) and theAC power supply may have a rated voltage of 100V-120V (depending on thecountry), which corresponds to the 100V-120V rated voltage of high ratedvoltage AC/DC power tools 5005. In countries having AC power supplieswith a rating of 220V-240V, the AC/DC power tools may be configured toreduce the voltage from the AC mains power supply voltage to correspondto the rated voltage of the AC/DC power tools (e.g., by using atransformer to convert 220 VAC-240 VAC to 100 VAC-120 VA).

In certain embodiments, the motor control circuits of the power tools5002, 5003, 5004, and 5005 may be configured to optimize the motorperformance based on the rated voltage of the lower rated voltage powersupply using the motor control techniques (e.g., conduction band,advance angle, cycle-by-cycle current limiting, etc.) described above.

The battery pack chargers 5009 have a rated voltage range of 17V-20V,with an advertised voltage of 20V, an operating voltage range of17V-20V, a nominal voltage of 18V, and a maximum voltage of 20V. Each ofthe low rated voltage battery pack chargers includes a battery packinterface or receptacle that enables the battery pack charger 5009 to becoupled to the power tool interface of one of the low rated voltagebattery packs 5006, or to the power tool interface of one of theconvertible low/medium rated voltage battery packs 5007. The batterypack interface or receptacle is configured to place or retain theconvertible battery pack 5007 into a low rated voltage configuration.Thus, the battery pack charge 5009 may charge both the low rated voltagebattery packs 5006 and the low/medium rated voltage battery packs 5007(in their low rated voltage configuration). This is because the 17V-20Vrated voltages of the battery packs 5006, 5007 correspond to the 17V-20Vrated voltage of low rated voltage chargers 5009. In one implementation,at least some of the low rated voltage battery pack chargers 5009 wereon sale prior to May 18, 2014. For example, the low rated voltagebattery pack chargers 5009 may include certain ones of DEWALT 20V MAXbattery pack chargers, sold by DEWALT Industrial Tool Co. of Towson, Md.

It is notable that the low/medium rated voltage (e.g., 17V-20V/51V-60V)convertible battery packs 5007 are backwards compatible with preexistinglow rated voltage (e.g., 17V-20V) DC power tools 5002 and low ratedvoltage (e.g., 17V-20V) battery pack chargers 5009, and can also be usedto power the medium rated voltage (e.g., 51V-60V) DC power tools 5003,the high rated voltage (e.g., 100V-120V) DC power tools 5004, and thehigh rated voltage (e.g., 100V-120V) AC/DC power tools 5005. It is alsonotable that a pair of the low/medium rated voltage (e.g.,17V-20V/51V-60V) convertible battery packs 5007 may be connected inseries to produce a high rated voltage (e.g., 100V-120V) that generallycorresponds to an AC rated voltage (e.g., 100V-120V) in North Americaand Japan. Thus, the convertible battery packs 5007 are able to power awide range of rated voltage power tools ranging from preexisting lowrated voltage power tools to the high rated AC/DC voltage power tools.

IV. Miscellaneous

Some of the techniques described herein may be implemented by one ormore computer programs executed by one or more processors residing, forexample on a power tool. The computer programs includeprocessor-executable instructions that are stored on a non-transitorytangible computer readable medium. The computer programs may alsoinclude stored data. Non-limiting examples of the non-transitorytangible computer readable medium are nonvolatile memory, magneticstorage, and optical storage.

Some portions of the above description present the techniques describedherein in terms of algorithms and symbolic representations of operationson information. These algorithmic descriptions and representations arethe means used by those skilled in the data processing arts to mosteffectively convey the substance of their work to others skilled in theart. These operations, while described functionally or logically, areunderstood to be implemented by computer programs. Furthermore, it hasalso proven convenient at times to refer to these arrangements ofoperations as modules or by functional names, without loss ofgenerality.

Unless specifically stated otherwise as apparent from the abovediscussion, it is appreciated that throughout the description,discussions utilizing terms such as “processing” or “computing” or“calculating” or “determining” or “displaying” or the like, refer to theaction and processes of a computer system, or similar electroniccomputing device, that manipulates and transforms data represented asphysical (electronic) quantities within the computer system memories orregisters or other such information storage, transmission or displaydevices.

In this disclosure, a “control unit” refers to a processing circuit. Theprocessing circuit may be a programmable controller, such as amicrocontroller, a microprocessor, a computer processor, a signalprocessor, etc., or an integrated circuit configured and customized fora particular use, such as an Application Specific Integrated Circuit(ASIC), a field-programmable gate array (FPGA), etc., packaged into achip and operable to manipulate and process data as described above. A“control unit” may further include a computer readable medium asdescribed above for storing processor-executable instructions and dataexecuted, used, and stored by the processing circuit.

Certain aspects of the described techniques include process steps andinstructions described herein in the form of an algorithm. It should benoted that the described process steps and instructions could beembodied in software, firmware or hardware, and when embodied insoftware, could be downloaded to reside on and be operated fromdifferent platforms used by real time network operating systems.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed. Numerous modificationsmay be made to the exemplary implementations that have been describedabove. These and other implementations are within the scope of thefollowing claims.

What is claimed is:
 1. A power tool comprising: a housing; an electricuniversal motor having a positive terminal, a negative terminal, and acommutator engaging a pair of brushes coupled to the positive and thenegative terminals, the motor being configured to operate within anoperating voltage range of approximately 90V to 132V; a power supplyinterface arranged to receive at least one of Alternating Current (AC)power from an AC power supply having a first nominal voltage or DirectCurrent (DC) power from a DC power supply having a second nominalvoltage, the DC power supply comprising at least one removable batterypack coupled to the power supply interface, the power supply interfaceconfigured to output the AC power via an AC power line and the DC powervia a DC power line, wherein the first and second nominal voltages fallapproximately within the operating voltage range of the motor; a motorcontrol circuit configured to supply electric power from one of the ACpower line or the DC power line via a common node to the motor such thatthe brushes are electrically coupled to one of the AC or DC powersupplies, the motor control circuit comprising: a DC switch circuitarranged between the DC power line and the motor; an AC switch arrangedbetween the AC power line and the motor; and a control unit configuredto control a switching operation of the DC switch circuit or the ACswitch to control a speed of the motor enabling variable speed operationof the motor at constant torque.
 2. The power tool of claim 1, whereinthe motor control circuit comprises an ON/OFF switch arranged betweenthe common node of the AC and DC power lines and the motor.
 3. The powertool of claim 1, wherein the control unit is configured to monitor afault condition associated with the DC power supply and cut off a supplyof power from the DC power supply to the motor.
 4. The power tool ofclaim 1, wherein the power tool further comprises a power supplyswitching unit arranged to isolate the AC power line and the DC powerline.
 5. The power tool of claim 4, wherein the power supply switchingunit comprises at least one of a relay switch arranged on the DC powerline and activated by a coil coupled to the AC power line, at least onedouble-pole double-throw switch arranged between the common node of theAC and DC power lines and the power supply interface, and/or at leastone single-pole double-throw switch having an output terminal coupled tothe common node of the AC and DC power lines.
 6. The power tool of claim1, wherein the DC power supply comprises a high-rated voltage batterypack with the second nominal voltage being in the range of approximately90V to 132V.
 7. The power tool of claim 1, wherein the DC power supplycomprises at least two medium-rated voltage battery packs and the powersupply interface is configured to connect two or more of the at leasttwo battery packs in series to obtain the second nominal voltage in therange of approximately 90V to 132V.
 8. The power tool of claim 1,wherein the DC switch circuit comprises one or more controllablesemiconductor switches configured in at least one of a chopper circuit,a half-bridge circuit, or a full-bridge circuit, and the control unit isconfigured to control a pulse-width modulation (PWM) duty cycle of theone or more semiconductor switches according to a desired speed of themotor.
 9. The power tool of claim 1, wherein the AC switch comprises aphase controlled switch comprising at least one of a triac, a thyristor,or a SCR switch, and the control unit is configured to control a phaseof the AC switch according to a desired speed of the motor.
 10. Thepower tool of claim 1, wherein the control unit is configured to sensecurrent on one of the AC power line or the DC power line to set a modeof operation to one of an AC mode of operation or a DC mode ofoperation, and control the switching operation of one or the other ofthe DC switch circuit or the AC switch based on the mode of operation.11. The power tool of claim 1, further comprising: a power switchingunit comprising a diode bridge and a controllable semiconductor switchnested within the diode bridge, wherein the AC and DC power lines of thepower supply interface are jointly coupled to a first node of the diodebridge and the motor is coupled to a second node of the diode bridge;and a control unit configured to control a switching operation of thesemiconductor switch to control a speed of the motor enabling variablespeed operation of the motor at constant torque.
 12. The power tool ofclaim 11, wherein the control unit is configured to sense current on oneof the AC power line or the DC power line to set a mode of operation toone of an AC mode of operation or a DC mode of operation, and controlthe switching operation of the semiconductor switch according to themode of operation.
 13. The power tool of claim 12, wherein, in the DCmode of operation, the control unit is configured to set a pulse-widthmodulation (PWM) duty cycle according to a desired speed of the motorand turn the semiconductor switch on and off periodically in accordancewith the PWM duty cycle; and in the AC mode of operation, the controlunit is configured to set a conduction band according to a desired speedof the motor and, within each AC line half-cycle, turn the semiconductorswitch ON at approximately the beginning of the conduction band and turnthe semiconductor switch OFF at approximately a zero crossing of the ACpower line.
 14. The power tool of claim 11, further comprising: a secondsemiconductor switch and a freewheel diode disposed in series with themotor to allow a current path for a motor current during an off-cycle ofthe semiconductor switch in the DC mode of operation.
 15. The power toolof claim 11, wherein the semiconductor switch comprises one of a fieldeffect transistor (FET) or an insulated gate bipolar transistor (IGBT).16. The power tool of claim 11, wherein the diode bridge is arranged torectify the AC power line through the semiconductor switch, but notthrough the motor.
 17. The power tool of claim 11, wherein the powerswitching unit is arranged between the common node of the AC and DCpower lines.